Rule 13: Watch the halls.
That dreaded moment when you walk around a corner and find that enemy ready to blow your block off. This is how to do more then just /alarm and die. Only a few people I know use this tactic, but I suppose more will after reading this. The "Z" key. Not very useful in most servers where it can only be used to make your head turn in different directions, but it can be used as a very important safety method in deathmatches. All you have to do is stand with your back to the opening of the hall/wall/or whatever, hold "Z" and turn your head either left or right depending on your direction. And boom! You've just spotted that camping blockhead, and you can be ready to kill and teabag him before he can say "LAG!!!1!". The best part about this is that you are unseen and protected by the corner, just make sure you don't accidentally make your blockhead bend down and give away your position.