Communication Is Key In Squad
A microphone should really be listed under the system requirements, as there's no HUD giving away the position of the enemy or clearly explaining where to run and what to protect. You absolutely have to talk to your teammates in order to relay enemy positions and find out where your squad members need backup.
The first thing you should do when joining a server is vocally announce your arrival and continue to check in every few minutes. The more people are talking, the better your squad will do in any given map. Listen in and follow your squad leader's instructions, as he or she will know where you should be putting pressure on the insurgents and where you should be fortifying and standing your ground.
Voice chat isn't just for planning assaults or letting squad members know where to aim their fire – you also have to verbally call for a medic when you are incapacitated. This is key, as you'll be tempted to give up and just respawn when you go down, but in Squad that's actually a bad tactic. Instead, wait for backup to revive you so you can help keep your allies alive longer.
Unless you all got killed by a grenade - don't immediately respawn!
If you don't have a microphone setup (and again, you absolutely need one to be successful in Squad), you can take part in inefficient text chat instead by tapping the “L” key.
The enemy team doesn't hear your chatter (although they do hear the in-game scream when you are incapacitated, which may give your position away), so don't worry about tipping them off to your plans. The only way to communicate with the other side is through global chat (accessed with the “J” key), although there's very few reasons you'd ever need to do so.