From the first part, we should know what the roles of the infantrymen are. But how do you perform them? In addition to that, I will go through some tactical procedures and basic skills for infantrymen. In short, we go back to boot camp.

Marksmanship

Although being the best shot isn't everything. That's what your there to do, why you're in the battlefield. To shoot the baddies and accomplish the objective. In PR, marksmanship is a tad different, as it attempts to use as much realism as possible in its ballistics.
The main property that affects your accuracy is deviation. Deviation is simply a 'steady' time. In real life, you need to steady your weapon to be accurate. The deviation simulates that. Depending on your stance, deviation can be longer (correct me if I'm wrong). But what are stances?

Stances are 3 different positions which soldiers use. They have a few different pros and cons. The 3 stances are as follows:

Standing:
This is the commonly used stance, and is pretty self explanatory, you are standing up on both feet.

Pros:
*Move at a decent speed
*You can sprint, increasing your speed even further

Cons:
*Large visual signature, the enemy can spot you more easily
*You move at a speed that catches the human eye easily
*Usually no cover facilitates standing
*More deviation time

Crouching:
In this stance you almost halve your height when you were standing, this is also known as 'taking a knee'

Pros:
*Reduce visual signature
*Facilitates lots of cover
*Less deviation time
*Speed is less likely to catch the human eye

Cons:
*Move slower
*Cannot sprint

Proning:
In this stance you lay belly down on the ground, it is also known as 'hitting the deck'

Pros:
*Visual signature is very low, very hard to spot
*Less deviation time compared to crouching
*Allows for cover behind low walls
*Much more stealthy, movement hardly catches the human eye

Cons:
*Move incredibly slow
*Cannot sprint
*Moving to a standing position from prone causes a small time in which you cannot fire your weapon

These pros and cons are based on the ideal situation for an infantryman. It's a bit wavy but I did my best.

After estabilishing that you need to wait a few seconds before firing for top accuracy you need to know how to aim.
Aiming is as simple as putting the tip of you aiming reticule on the target. But then you need to take into account several other things. Such as sights and bullet drop.
There are 3 sights in PR:
*Iron sights, metallic sights with usually 2 sights to make up the whole sight
*Aimpoint, a red dot sight that is less obstructing than the iron sight
*Scope, a magnified optic sight that allows for engaging targets at long ranges

Iron sights have a small sight near the back or stock of the weapon, and imbetween that sight, further down the barrel, is the tip sight you actually put the target on. The iron sighted weapon usually obstructs your view.
Aimpoint sights use one red dot sight. All you need to do is put the target on the red dot in the centre of the non-magnified scope. It is designed to decrease obstruction of view that 'irons' give you
Scopes are magnified, there are many different sights. But the main thing you're looking for is a tip in the centre of the scope, some of the scopes use proper crosshairs that I personally consider easier to aim with, such as the PLA standard rifle. Most of the other sights have a triangular tip, you put the target on that tip, or with crosshairs, you put your target in the centre where the lines in the cross intersect.

Remember that shooting and moving affects deviation, so once you are looking through the sight and you move, you have deviation increase. After you shoot you also have deviation raised again. In close quarters, you don't need to count on deviation time as the bullets will be accurate enough to hit anything in close range.

We need to identify lastly 'zeroed' ranges and bullet drop. I feel like I'm really going on and on, so I'll try to make this quick. Here are the weapon bullet drop ranges:

Assault rifles: Bullet drop after 300m
Sniper/marksman rifles: Bullet drop after 600m
Light AT weapons: rocket drop usually comes into effect over 150m
Light Machine Guns (Auto riflemen): Bullet drop after 300m

Any targets you engage before the above listed ranges, you can simply put the tip of your sight on. After those ranges, you have to aim slightly above your target to score a hit.
Grenadier sights uses ladders. Usually, the ranges in ladders differ from 70m-100m. Grenades launched from under-barrel grenade launchers require around 50m to arm otherwise they'll hit without affect.
Snipers, marksmans and LMGs take longer deviation time to be accurate. Assault rifles and AT weapons usually take 2-4 seconds.

Skills for infantrymen

Some skills in general for infantrymen should be:
*Maintaining situational awareness, I.E. staying aware of your surroundings
*Seek cover whenever possible, this is anything that can stop bullets, things like wooden shacks or tin fences or market stalls don't provide solid protection against bullets
*Know your squad members, know their voices and roles
*Keep your spacing when moving in a squad or fireteam
*Try to identify cover positions, or anything in the field that can you give your squad a tactical advantage
*When wounded, identify whether you are still combat effective. If you screen turns black and white or your character begins breathing heavily, pull out of the fight, otherwise you will very soon die. If you take one hit and don't encounter the effects mentioned above then you should keep fighting
*Leading is easier when the target is 45 degrees on an oblique angle, sort of running diagonally. It is hard to hit targets that are moving perpendicular to you
*If in doubt whether someone you have targeted is friendly or enemy, consider it as a friendly, taking a friendly casualty is much worse than allowing an enemy to pass by

Medic skills
Skills for the medic would be:
*Identify who is wounded, how many are wounded, who is dead and who is bleeding and needs medical attention
*Prioritise your wounded, try to save people with important kits like ATs or Auto Rifles, and also prioritise based on the amount of time the person has been critically wounded
*When reviving multiple wounded, give each one a field dressing (in-game sometimes refered to as a 'patch'). This will allow them to sustain life for long enough for you to get around to healing them
*Use smoke to coneal bodies that are out in the open without cover
*Give people who you revive directions to where they need to move to get behind cover, this will allow you to heal in a bit better safety
*Give orders to friendly soldiers to supress or kill enemies that are preventing the revival of WIAs. Getting friendlies up is your job, and you must do whatever it takes to accomplish that
*Stay behind the force, stay safe and don't get into the fight unless you absolutely have to

Rifleman AT skills
*Know the armour weak points, target the engine or hood area of jeeps and trucks and the side, rear and top armour of APCs
*Try to setup in a place where leading targets is a bit easier, targets moving perpendicular to you are much harder to lead, but targets moving at a slight oblique angle (about 45 degrees angle on the armour) can be easier to lead
*Make sure that you are in clear view of the target, if your sight is just over a wall, you will hit the wall
*Listen for armour or jeeps
*Have the AT out as soon as you hear armour or vehicles

Automatic rifleman skills
*Use your tracer rounds to help you correct your firing, look at where the tracer rounds land, or look like they're landing, and adjust your fire
*Auto rifles are meant to be used at range, so do so, going in close eliminates this ability
*Auto rifles are a bit better in CQC, but it's still better to use them at distance
*Try to supress rather than kill, if you can't hit the target but you see that their heads are down don't try to move to another position unless directed, you are allowing your friendlies to move in and finish them
*Use undeployed mode for targets 0-100m away. Use deployed mode more defensively for preferably longer range targets over 100m away

Rifleman skills
*Move into any position where you will be able to kill, as long as you stay close to your squad or fireteam, unless directed otherwise
*Use your grenades to kill enemies in buildings or fields before entering
*Choose you weapon (CQC or Scope) dependant on the situation the squad leader describes will be happening, if he says you will be going into a village, get an CQC sight version, not a scope
*Use extra ammunition only when you are at low ammo, I.E. 1 or 2 clips left or when directed

Officer skills
*Inform your squad members of any new intel received
*Look for any natural or manmade areas that can give you a tactical advantages
*You may be the leader, but that does not mean you do not lead from the front, leading from the front allows you to identify the tactical situation quickly and make life-saving decisions based on that knowledge
*Lead by example, stand up and shoot when getting shot and your squad members will likely follow
*Take responsible risks
*Keep in co-ordination with other friendlies and know where other friendlies ,that are nearby, are approximately

Marksman skills
*Try to find a position that gives you cover or concealment while still allowing overwatch of an area
*Your weapon is designed for long range, don't go into a position where you are likely to receive contact from 50m away, such as a city or village unless directed otherwise
*Target high priority targets, like officers, medics and auto-riflemen

Grenadier skills
*Use ranging from the Squad leader markers for direct fire on enemy positions
*Use smoke grenades to help identify ranges then use that knowledge to fire fragmentation grenades on the smoke
*Use launched smoke grenades to mark enemy positions or to block their initial view, like a pronlonged flashbang effect

Procedures

The final part of this 3rd edition is this. The last thing to view will be formations, contact reports and combat drills.

Formations
*Formations are positions which infantry squads and fireteams move into as a whole which give the certain team performing that formation a tactical advantage.

Line
*Basically follow the leader
*You follow the person infront of you, keeping a distance of about 5-10m, whatever they do you do, if the crouch you crouch, if they prone you prone and so forth
*Try and look in different arcs to the person infront of you, if the are looking left you look right, look somewhere they're not

Column
*You are moving in a line, but instead of having people infront and behind you, they are to your left and right
*This allows for a large mobile firing line that is ideal for directing lots of fire onto a position

Wedge
*Like a column, but the people to your left and right are behind you, in an overhead view this looks like an arrowhead or triangle
*Allows for the ability to direct massed fire in any direction with at least half of the entire force which is using the wedge

Parallel line
*You move in a line which is parallel to another line column up to 100m away
*This allows for the two units using the parallel line to cover a larger area
*Having a line formation parallel but ahead of another line formation allows for ability for one element to scout ahead

Diamond
*A formation which is meant to be used when a small unit is halted
*the diamond allows 360 degree coverage and provides top security for the unit when they are halted
*This formation can also be used on the move

5 meter spread
*Formation which is meant to have units spread out sporadically at least 5m away from eachother
*Ideal for clearing of forest or jungle
*Also ideal for covering other closed in areas, like villages

Contact reports
Contact reports are those which allow you or friendlies to convey a lot of information about a spotted enemy very quickly
The main things needed in a contact report is:
*General compass direction (North, south etc)
*Compass bearing (e.g. 285 degrees)
*What the enemy is (e.g. enemy infantryman)
*What you are currently going to do (e.g. are you going to shoot him, observe him or find cover)

Some other little ingredients to make your contact report even more informative:
*What kit the enemy has (if an infantryman)
*What the enemy appears to be doing (scanning for targets, moving across a road)
*If he is moving, how is he moving (e.g. ... moving north to south)

Combat drills
Combat drills are pre-practiced drills which are used when certain contacts are engaged in certain circumstances. They are also known as 'actions on contacts'.

Unexpected contact drill
During duty you'll likely be engaged by unexpected contacts, when moving as a fireteam or whole squad, the actions to do are as follows:

*After receiving fire, each squad member should seek cover or (on direct of squad lead/fireteam leader) to go prone and 'hit the deck'.
*Begin scanning the surrounding area and horizons for the enemy, make sure you cover 360 degrees around and try to look at something your squad members are not looking at
*After having identified the agressor, alert the squad or fireteam
*Find cover that protects fire from that direction
*An assault element begins moving towards or flanking the suspected position of the enemy while the support element provides overwatch
*Assault element eliminates enemy and support element holds position and covers area until assault element returns or unless directed otherwise

Known contact drill
You will also be given intel on enemy locations, you then act how the squad leader or fireteam leader thinks best to assault that position.

*Move to a pre-determined point to engage the known location of enemies
*Once arrived, find cover covering in direction of suspected enemy force
*Scan the area for enemies
*After having identified enemies, support element will move into fire support positions
*Assault element begins to assault to kill enemy forces, during this support element provides supressive fire
*Assault element eliminates enemy force
*Assault element returns to support element which holds position until assault FT is back

House-clearing drill
When you need to clear a building, if you do so in an organised fashion you can clear the building with minimal casulaties

*Target building is identified
*All or most possible entrances are identified for breach of squad
*Infantry 'stack up' (I.E. line up behind one another) next to breach point
*Grenades are thrown to stun or kill enemies inside
*After grenades explode, infantry breach and move in a tight line formation and scan different arcs, killing any enemies in sight
*After building has been cleared, breaching teams exit from their breach spot

If buildings have multiple floors, you need to be sure that the below floor is clear before moving onto the next one.

Ambush drill
Sometimes you will find your squad or fireteam will wander into an ambush, knowing what to do in an ambush is vital as you start off with a very high chance of death.

*Find any possible cover and immediately return fire on any enemies
*Fire into areas where you hear enemy fire coming from if you cannot hear them, you just need to supress the enemy long enough to get out of the kill zone
*Try to keep moving, the objective is to get out of the kill zone, or the place where the ambush team is focsuing all their firepower
*After getting out of the kill zone, attempt to link up with friendlies to kill the ambushers
*After ambushes have been killed or have retreated, identify your wounded and dead, and get immediately to treating those casulaties

This is why sometimes it's better to have elements moving behind eachother, so that they don't all get ambushed and can respond to kill enemies

This concludes part 3, next part will be: Cover, concealment and combined arms

I couldn't really fit cover and concealment into this post. So I'll squeeze it in in the start of next part.