I guess I have a few tips to add as well since I've played the PS3 version for quite a while:
- Don't sprint (press L2) unless you're sure no one is around - such as at spawn. It lets the enemy know your (and possibly your whole team's) location and they can easily swarm you or flank you. However, this can also be an advantage. You can sprint to get an enemy to follow you and then place some bombs in their path to down them. You can also sprint back to your team if you get into trouble, have the enemy follow you, and they get lit up by your team. Note that if you are in active combat, sprinting doesn't matter as much, since the other team knows where you are already.
- Always mark enemies. You mark enemies by pressing R3 when you're aiming at them. Marking alerts your teammates to where an enemy is on the map. This is especially helpful if you have the Hawk-Eyed 2 or 3 perk, as the enemies light up in red, making their outlines and actions visible to both you and your teammates. There may be enemies you can't mark - as they have the Covert Training 3 perk. If this happens and you're using a mic, tell them where that enemy is. Note that if you are trying to be stealthy and flank another team, you shouldn't mark anyone, as they'll hear your voice marking them and will more or less know where you are.
- Revive carefully but diligently.
- Basics: Frequently, you or your teammates will go into a downed state because they took too much damage. When this happens, you can revive them by holding Triangle over them. This fills up a meter above their head in blue. When it is full, they are revived. Note that the more people you have reviving someone, the faster the meter fills. However, you only have a limited amount of time to start reviving someone, as once the red bar above them runs out, they are dead.
- In combat: You always want to revive your teammates when possible. However, you have to assess the situation before you start to revive someone. If you see enemies rushing toward you, that is not a good time to start reviving someone (unless you have reviver 3). If you see an enemy with a bomb or molotov near you, that is not a good time to start reviving. If your teammate is in open space and there are enemies around, don't revive. If none of that is happening, then reviving is probably safe to do.
- General reviving tips: 1) Crawl behind cover. Your teammates will be less likely to revive you in open space. 2) If you and one enemy down each other, tell your teammates over mic and they will probably come and save you. They won't if they think there are more enemies there and they'll get ambushed. 3) Move the camera around while you're reviving. This will help you see if anyone is coming near you and you can decide whether or not to stop reviving. Note that you cannot shoot or heal yourself when you are reviving someone. You can also get downed in that state.
Alright. That's all I got for now.