How not to die 101:
1. Never run in combat, (only for travel)
2. Stay out of the open
3. Stay along the edges of a confrontation zone, never be in the middle
4. Before spawning on a squadmate, take a second to make sure he isn't about to die
5. Always have an alternate route, stay behind cover
How to kill 101:
1. Take your corners slow,
2. Get around the enemy, and flank
3. with #2 in mind, take a second to aim and make every shot count
4. Burst fire with your weapon, don't spray and pray
5. Pick the right weapon, a shotgun for inside a building, and an assault rifle for streets
And lastly, Adapt, the most important thing to do well. Reflect on what you did in a match, ask, what was the biggest problem in that match? why did you keep dieing? Were you running straight at the enemy? or were you going around? etc. Then, correct the situation.
P.S. If a team mate dies while going around a corner (or area), DO NOT do the same thing, go around, flank.