1) You will die. Accept this. Make peace with this. Fight to the bitter end, true to the spirit of the franchise, knowing that:

2) Mission failure still gives you xp, while

3) Quitting gives you NOTHING.

4) The plasma cannon is bad. In games with no friendly fire, it diminishes broodlord encounters to a minor distraction, and in games with friendly fire, it diminishes everyone's health to a minor puddle on the floor. Try the Spear instead. Pewpew.

5) If you're joining games because you can't or won't host, it is perfectly acceptable to enquire as to the rules and/or difficulty. It is not acceptable to criticize the choice.

6) If you're hosting games, be a good host: Let people know if you're planning on only running one map and then quitting, wait a moment at the end of mission screen before quitting, and provide hot beverages as needed.

7) Thou shalt press the medic button once, and only once. Spamming it does not take time off the apothecary's cooldowns. In situations where it genuinely appears that the apothecary hasn't noticed your plight, you may consider pressing the button once more, apologetically.

8) If you play as assault, you are expecting other teammates to take out turrets and hybrids. Nobody forced you to pursue your knightly fantasies - keep this in mind before complaining.

9) If the room you've just entered has Tyranid symbols in it, locking the door means you've just locked yourself inside a room with Tyranids. Good job!

10) If the room you've just entered has another door up ahead, and your teammates have already gone through it, don't lock the first door: Catch up to the others, and lock the second door.

11) If you're transitioning from a narrow corridor to a big open space, and you're locking the door to the narrow corridor behind you, you've just locked yourself in a big open space with a potential Broodlord. Extra special good job!

12) Shoot the bell. Do it. You know you want to.

13) If nobody is visibly leading, it means your teammates are sheep. Pick a direction and move before you all die.

14) If the map turns fuzzy, shoot the empty corridor ahead of you. If you hit nothing, shoot the empty corridor behind you. If you hit nothing, YOU ARE ABOUT TO DIE. BLOCK.

15) Block.

16) Don't stand still. A single step to the left could mean the difference between a spike through the face, and a spike through the arm. You can lose an arm. You can lose both arms. You only have one face.

17) Don't be that guy who steps in front of a teammate who is already shooting at a target, to shoot at that target. Nobody likes that guy.

18) Do not turn your back on the enemy, unless your teammates are covering you.

19) Watch the map.

20) Watch the map.

21) Watch the map.

22) Watch the map.

23) Watch the map.

24) Your teammates are now in a different room because you didn't watch the map, and you're going to have to turn around and sprint to catch up: See point 18.

25) One of your teammates is now dead because he didn't watch the map, and didn't notice that all of the little green arrows were pointing in one direction, and not at the motion detected in the corridor behind them.

26) All of your teammates are now dead because you didn't watch the map, and then somebody else didn't watch the map, and then the last survivor managed to lock himself in a room full of Tyranids and you're all now staring at the mission failure screen... remember points 1 to 3.