After a couple of years and still, some rounds I'm top of the leader board, some rounds, at the bottom.
Great ideas have already been suggested.
It takes a while to learn what the bad guys look like, so it will be a bit before you can pick out those who are hiding in good spots and nailing you.
Learn to look for muzzle flashes and to listen. Dash from cover to cover and then take a sec to asses the situation.
In the open, you will likely die. When you have to cover open ground, sprint and zigzag. Let another teammate go first and see if they come under fire, lol. Crossing open ground with a bunch of other teammates improves your chances. The School of Fish technique.
Don't be repeatable. Don't stick your head out in the same spot. Always move around after a shot or two.
Don't run through smoke
How easy it is to stay alive is also very dependant on the quality of your team. If it's good and steam rolling the enemy, your arty will be making the other team miserable and your teammates will be holding the important positions and pinning the other guys down. You'll feel invincible, you can take risks and stay alive.
If you're on the other side though, no matter how good you are, you'll feel like you can't take a step without dying from an invisible enemy.
Being in the cap will help your team and get you points..... Unless you are a marksman or MG, sitting back and sniping helps no one.