ALL comms should be kept to an absolute minimum.

However, "absolute minimum" is an oft-miscalculated value. In some cases, it's a LOT of talking, and in others it's near-silence.

Let's explore it.

First, the game offers LOTS of comm tools you can use without using VOIP. Most of these have these advantages over VOIP:
1. They integrate with your HUD
2. They don't drown each other out (you can hear/understand/assimilate multiple messages simultaneously)
3. They are more easily and quickly performed in-game than speaking

With those tools, you don't actually have to speak often.

As a Commander, your primary limitation is that you don't know who else you're stomping on. Use all the outstanding commander tools you have, and speak as rarely as possible. Be concise and quick, and if possible, get the SL's attention first so he can tell his squad to stfu for a sec :
CO: "Commander to Squad 6, over."
SL: "Squad, clear comms." "Go, Commander"
CO: "blah, blah, and also, blah."
SL: "Uh.... roger blah, Commander. Out" "Squad, open comms."

As a squad leader, you should have control of comms. You know when your commander is talking, and you know when your squaddies are talking. As such, here are your general rules of thumb:

1. DO NOT _just_ be an "order-pipe" for the Commander. Think of the CO as telling you "what," and the SL as telling you "how."
The SL role is EVER-SO-MUCH-MORE important than passing on the COs orders. To give the "how" you need VOIP.

2. DO give the squad explicit tactical orders. You have much more to tell the squad than "Go here. Attack there.". It's all about making the squad an effective unit. How well you make the squad work together is the measure of your success as an SL. To do that, you should use VOIP for specific orders for each squad member (or fire-team) that the in-game tools can't help you with.

3. DO NOT chit-chat. The squad members, during a lull in the fighting, may occasionally make a remark or cut up with something funny that they saw. This is cool, and this is a game. But you set the example, and the squaddies will deviate a bit from that. So if you set it loose, they will regard it as "really loose," and you will have comm-hell. Keep YOUR chat tight, and theirs will be just loose enough to be fun and relaxed.

4. DO talk. For Pete's sake, give your squaddies purpose and unity and make sure they're all focused on ONE job at a time. To do that, your use of VOIP will include making sure everyone is on the same page, working together.

5. DO NOT leave your squad in a tactical-vacuum. Keep them informed of what the squad is doing, why, and how it fits into the big picture. You must use VOIP to do this.

6. DO NOT flood the comms with your talk. Period. Say only what is necessary. That will amount to enough by itself, if you count all the above items as necessary (you should).

As a squad member, follow the same rule-of-thumb. Use in-game tools as much as possible. For everything else you MUST use VOIP. And, you should use VOIP as much as you need to. And no more. Some examples:
- (You died w/out being able to "spot" an enemy) "Enemy squad to Northwest"
- I'm going to man the AA gun.
- Medic down.
- They're flanking us to the south.
- They're taking back the flag we JUST left.