How to be successfull in Multiplayer
1. Don't stop moving. This doesn't mean you have to always be running, great distances, but if you camp a spot, side step around a bit.
2. Be unpredictably unpredictable. If you make a straight line for a door, you're dead. If you zig zag strafe left and right towards it, you're dead; but if you stutter step, and get creative with it you'll more often stay alive than the guys who just bunny hop and run in a straight line. (Aim ahead, wait, click, it's that easy)
3. Learn to use every weapon. You have time, no rush. Force yourself to play with every weapon. Hell, pick a weapon and play that entire round with it. Learn it's limitations, aim and advantages. That way, when you are facing the enemy who is using it, you know what he can and cannot do, and what he's waiting for you to do so he can use it on you.
4. Learn the audio of each pickup. As in past games, each item has a unique and distinct sound. Learning this can make the diference in your life expectency. This goes hand in hand with #5.
5. Learn the maps. Learn them front and back. Learn it well enough that you can run around the map running backwards. Know the routes out and into every room. Know the choke points, know where to hide. Once you can run it backwards, learn the locations of pickups. A cluster of health can give away a players location if you or your enemies know where that cluster is, and hear it being picked up.
6. Know your health at all times. Know which weapon does what damage to you, and how much of it. Practice with a friend and make note of the damages that happen. Know that if a rail shot does 100 health, you'll need 100 health and 1 armor to survive, or 1 hit and you're out. Take advantage of this. that 1 armor gives you the safety of requiring an enemy to hit you 2 times instead of 1, which can give you an escape if you are lucky. Staying alive means no score for the other guy.
7. Spectate good players. Pay paticular attention to what weapons they keep idle while they explore, and what weapons they coninstantly use, as well as where they patrol, defend and fight.
8. fight or flight: know when you're superior or inferior. If you have 42 health and no armor, you wouldn't attack someone armed to the teeth and full armor now would you? Find some health and a few armor (like #6 said) so you can atleast stand a 2nd shot. If you know the enemy is hurt, be very agressive and get to them before they can recover. But always, know when to get the hell out before you die.
9. Don't be a hero. There is no shame in dying, if you are trying. But rambo rushing enemies will get you dropped. Realize that each weapon makes distinct sounds, and often projects light and particles that give away your position. Conserve your ammo, and be smart. Your position can be your greatest advantage. Why blow it by spamming rockets out of the shadows or from a pearch above. Try to use weapons that do great damage with minimal exposure. Think before you shoot. It's better to let an enemy pass you by unaware and get them from behind, then to start blasting away while they can shoot back.
10. Be respectful and players may take you under their wing. Calling people noob, telling them to stfu, calling them hax, cheaters, etc. This kind of behavior will stonewall you from learning. 99% of the players seemingly unkillable are not cheating. Most of these players played for years. Playing on newbie servers may stroke your ego, but when you can, step up to servers that have players much better than you. Spectate them and become friends. Show an eagerness to learn, and have an open mind. You just may find than in a few weeks, you're already on your way to being a quake god. If another player can do it, so can you, remember that.
11. In every map there is at least one armor pickup. Memorise where it is. Take it, and count how long until it reappears. Now when playing against people, get the armor immediately, go off, but return just before it reappears. This way you have a HUGE advantage over other players.
Thanks to Mr. Do!! at the PlanetQuake forum