Crouch often. Always crouch when you can. Why? Because it stuffs you lower down, rather than a big ass dude running by, theres a lesser chance that you will be SEEN. But that doesn't mean crouch in the middle of a battle, unless it's crouch jumping. Crouch in consideration, thank you.
Jump/crouch jump! I know this pisses alot of people off, but, it works. Set your mouse sensitivity to a decent speed, so you can control yourself yet look around without flinging the mouse accross the room. When your in battle, usually close range, jump up and down while running. This sounds stupid, but it actually works. Your body jiggles and stuff, and it's harder, DEFINATELY, to get a headshot at least. Also, crouch jump. If you master the jumping, then you can crouch jump. After you jump in the air, crouch and come out of crouching. This makes your body do all sorts of stuff, and angers alot of people because they can't kill you. Usually resulting being called a noob. Or a nigger. Or a jew. NO OFFENSE.
Camping. Camp in a safe distance, and always remember, people are invulnerable for a certain amount of time, meaning they can't die. So don't just blow your cover as soon as someone spawns, you will just end up dead.
HIDE BEHIND STUFF! Take advantage of glitches and stuff, in which give you the upperhand. Hiding behind something will always give you a better chance of surviving, via running around in the open..
Lay mines! Watch your opponents usual trips, watch where he goes, and tries to find you while hiding. When you have the chance, lays some mines behind doors and his usual path, he/she wont expect it yet they make a loud boom.
Grenades, grenades, grenades! In my opinion, grenades are a pros best weapon. Throw them, but, dont hit yourself or your team. If you throw them right, you'll usually get a 1 hit K.O. Usually throw them a little farther than you would think, people usualyl retreat after seeing a grenade.
Don't call people a noob. Reason behind this, is sometimes they unleash a power so wicked that they can either..
1.Bust out some elite hacks
2.Become pro instantly
3.Cuss you out in a different language.
Don't run into open area's. Always ****** your surroundings before you just rush out into the death valley.
Don't stop to type in the open. Don't stop to type in the open, because that's usually some of the best times to kill someone. Usually people think it's cheap, but hey, it's the way to win.
Don't walk into mines.. If you see them, shoot them from a safe distance. Don't walk into them hoping you will survive.
Don't go straight into a grenade.. Best chances are, your opponent will throw a grenade to short, or to far. Usually best to go left or right. For safety.
Don't enter a room filled with pro's, thinking you can win easily this way. Most of the time they are also versing veterans, and you'll lose. OR, you'll suck and they'll cuss you out in a different language. One or the other.
Only thing i don't like about mines, is that there is no way to tell if its one of your teammates or an enemies. So sometimes i'll shoot one of my teammates mines without knowing, and they'll get pissed at me.