Here's some of my tactical rules I live by for UT.
Rule #0, Don't have a bad connection: Lagging sucks.
Rule #1, Know how to aim your gun: If you can't aim properly, then nothing else matters, you're gonna lose.
Rule #2, Know the maps: Knowing the maps is key. This will allow you to know all the routes, exits, terrain/cover, area names, etc.
Rule #3, Know how to move/jump properly: Jumping/moving properly makes you faster and a harder target to hit.
Rule #4, Have experience: This allows you to determine good strategy and make good tactics. This is especially helpful in team matches.
Rule #5, Situational awareness: Look at your mini-map, utilize your sound as to hear enemies, etc.
Rule #6, Be a team player: Med others, help outnumbered team mates, and know that sometimes you must sacrifice yourself to win the match.
Rule #7, Know your limits: Inversely, sometimes it's better not to help outnumbered team mates, as you might just end up wasting your life as well.
Rule #8, Have fun: If the game stops being fun, stop playing the game.