If you are looking for realism and immersion in your ArmA experience then you should read this article that I spent time making. And this is all from my experience.

Make sure you make two modfolders with the @ symbol with any name of your choice before you start downloading stuff. Also remember to put a folder named "Addon" in each of your modfolders or else your mods will not be activiated once you start up ArmA. The first modfolder should contain all of your game tweaks and modification files while your second folder should contain all your replacement files to replace your ArmA vanilla files. Make sure you know which ones go where.

In your target box make sure it looks similar to this
-mod=DBE1;@Folder Name 1;@Folder name 2 -nosplash(this is if you dont want the game intro in the beginning and you just want to be taken to the main menu)

First go to your Arma profiles wherever that is located and find your profile. Search for the class "Difficulties" and replace them with the following parameters(or copy and paste):

class Difficulties
{
class regular
{
class Flags
{
Armor=0;
FriendlyTag=0;
EnemyTag=0;
HUD=0;
HUDPerm=0;
HUDWp=0;
HUDWpPerm=0;
AutoSpot=0;
Map=0;
WeaponCursor=0;
AutoGuideAT=0;
ClockIndicator=0;
3rdPersonView=0;
Tracers=0;
UltraAI=0;
AutoAim=0;
UnlimitedSaves=1;
MaxCustomFileSize=33554432;
MinErrorToSend=0.080000;
vonCodecQuality=10;
VonID=1;
NetStats=1;
DeathMessages=1;
};
skillFriendly=1.000000;
skillEnemy=0.500000;
precisionFriendly=0.500000;
precisionEnemy=0.030000;
};
class veteran
{
class Flags
{
Armor=0;
FriendlyTag=0;
EnemyTag=0;
HUD=0;
HUDPerm=0;
HUDWp=0;
HUDWpPerm=0;
AutoSpot=0;
Map=0;
WeaponCursor=0;
AutoGuideAT=0;
ClockIndicator=0;
3rdPersonView=0;
Tracers=0;
UltraAI=1;
AutoAim=0;
UnlimitedSaves=1;
MaxCustomFileSize=33554432;
MinErrorToSend=0.080000;
vonCodecQuality=10;
VonID=1;
NetStats=0;
DeathMessages=1;
};
skillFriendly=1.000000;
skillEnemy=0.600000;
precisionFriendly=0.500000;
precisionEnemy=0.030000;
};
};

Make sure you backup your original files before you save it cause I didint and I had some problems.

This will set the game to rather higher standards than the regular in game difficulty options.
3rd Person will be disabled
No crosshair
And rather tough, clumsy AI in regular mode


Mandatory Add-Ons

Gameplay and Graphics Enhancements

GMJ Sight Adjustment

Functional Ironsight for AT4 and RPG

MaddMatt ArmA Effects

JTD Smoke Effects
Note: This mod will conflict with MaddMatt ArmA effect's, in order to fix that
the smoke effect will have to be loaded after MattMatt's effecs. To do that just put the Smoke effects files into your second modfoler instead of the first one and you should be good to go

VF AI Extension

NW Realistic Ballistics

NWD Tank FCS

GLTDII RangeFinder

Sharper Recoils and Real Rate Of Fire

Wind Deflection

Durgs Vegetation Fix

Proper Gameplay Addons
Theres a whole bunch of them but I recommend you browse the site to see which ones are best for you

6th Sense
Pack 1
Pack 2
Pack 3

Addons Used:
SIX_Misc.pbo
SIX_Repl_Reloadtime.pbo
SIX_Repl_WeaponSway.pbo
SIX_sys_ai.pbo
SIX_sys_suppression.pbo
SIX_Tools.pbo
SIX_Tracers.pbo
SIX_UI.pbo

True Mods

Addons Used
TrueFov-Accurate v1.0.pbo
TrueHeadMovement v1.0.pbo
TrueIntro v1.0.pbo
TrueMovementSound v1.0.pbo
TrueNVGoggles v1.0.pbo
TrueInGameUI v1.1.pbo

RVN Compass Mod

Red's Fix

ArmA 1.14 Compact Fix

Fixed NightVision

TCP Animation Pack

High Quality Weapons And Character Files

If you like the US Army:
1st Infantry Division

If you digg Marines
Fidelis Marines
The best marpat i ever seen

SLA Redux Pack
This pack is a good replacement for the regular SLA textures very detailed

Fidelis Russians
Or For your OpFor replacements you can use the Fidelis Russians which are also made by the guy who made the marines above. These are a little more conventional than the SLA Redux soldiers.

You will need these for updated weapons textures
Rebus Italian Weapons
which include the MP5's and G36's and such

RH M4/M16 Pack

RH AK Pack

This is not mandatory but I high suggest you get the Extended Event Handlers to supplement your experience.

Mateck's M1A1 HA
This is the best ever made Abrams tank I have seen so far. It comes with decals and different layouts so you can customize it. They will be updating this soon with T.U.S.K armor and more goodies.

SPD Vehicles

SLX Vehicles
This will add animations to ingame vehicles that ill let Doors open, antennas sway while moving, mounted weapons have working parts. This is a must-have!

Replacement Files

Realistic Designation

Unique Models For Different Ammo Drops

And then you will need the Infanty Weapons replacement pack that replace's all of the standard textures with the ones above. Note: this will not affect you during Multiplayer. This is client side

HIFI Sound FX
Mark XIII's outstanding "HiFi Sound FX" is the most realistic and consistent sound mod so far. It keeps many of the weapon characteristics and delivers a great combat atmosphere. This is highly reccomended

Also try
FROMZ FFAM
Great Movie flair like sounds, consistency issues but awesome!!

FDF
Adds that shooter feeling

AACF
Very neat high quality soundscape

Or If you want to combine them all use mrcash2009's Mixed Sounds config

Extended Voice Addon
This replaces those cheap, robotic vanilla sounds with real high quality coherent radio chatter

Dynamic AI Sound

High Quality Sky Replacement

ECS

For those of you that want to use ECS (Enhanced Configuration System)
Download it here

Make sure you also download the Themis Compatiblity Fix to make it work with extended event handlers

- When you done with the installation, doulble click the @ECS folder, then go into the addons folder.

- Make a folder called Disabled Add Ons inside that folder

Move these files into that folder
-ECS_Armory.pbo
-ECS_Quiet.pbo
-ECS_Tracers.pbo

Make sure you run ECS first for your mod loading order
mod=DBE1;@ECS;@General;@Replacements

This will be updated frequently as there always new addons and things coming out for ArmA