- when you are dead, don't use teamchat (Y), because only dead team-mates will see what you write. Those still alive cannot see that. Use normal chat (T) instead. This is a very common mistake seen on servers.
- turn on Subtitles in your in-game settings (option is disabled in some language versions of game, but at least in English version it is available). When you hit someone with flash or stinger, you will see his name in chat so you know if it was your team-mate or enemy.
- when you play with helmet and you get hit by gas, use any voice command (like Roger, Where is the VIP?, etc.). That usually makes you stop coughing and thus you have higher chance of hiding.
- changing gun from primary to secondary and vice versa is faster then reloading. Keep that in mind when you run out of ammo in the middle of shooting.
- if your chat does not work (you press ENTER but the message is not sent) press left Alt. After you can should be able to send your message again.
Note that as of today, you can see all hint articles published so far by clicking the "Hints" in the main menu.