Avoid futile attempts – Don’t waste your ammo on enemies that are too far away. If they don’t see you yet, just wait - you’re better off flanking and surprising them than giving away your position by carelessly firing in their general direction.
Melee with care - Running directly toward another player, finger itching to hit the melee button, will almost always get you killed. The winner of a melee duel is not determined by who pressed the button first - it is determined by shield levels (see video).
Your best bet is to rely more on your weapon’s primary function than the butt of it, using melee attacks when the opportunity presents itself organically (and it will often), or when you’ve managed to flank someone for an assassination. If your opponent runs toward you, you have him.
Also, you will notice that you can press the melee button well before you generally think you need to and still get the kill, so if you aren’t having any luck, try hitting the button half-a-second sooner.
Tip: There's nothing like a good stick, but spend too much time aiming grenades and you'll be the only mangled body on the ground
Shoot, grenade or grenade, shoot? - If you’ve struggled with grenades, try to keep in mind that (unless you stick someone) they can’t take anyone out on their own. There are two predominant strategies when using grenades:
1. Run backward while pumping your enemy full of bullets, then, when your shields are low, drop a grenade and run away to recover. If you’re lucky, they’ll run right into your little present in pursuit, and the explosion will be enough to finish them off.
2. Start tossing grenades as soon as you encounter an enemy, and then go in for the kill once they’ve been weakened.
Generally you’ll know which method to go for depending on the situation. Experiment and practice – you’ve got to know exactly where to bounce a grenade in order to catch oncoming opponents in its blast.