I know theres a bunch of guides out there to help noobs out but I want to add my 2cents in on a few things.
1) Mouse Sensitivity is very important... Set this HIGH but not all the way.. On a scale of 1-10 id say a 7 or 8 is what you want.
2) Stick with the same weapons every time you play... When I 1st started playing I switch between Bar, Tommygun, m40, m44 ect and never got use to one.. They all shoot different... Now all I use is the M44 as a German or M1 Grand as American.. Unless im on a sniper map... I try to stay away from the Russians and British but if i do get stuck with those I look for a M44
3) Aiming took me a while with the crosshairs getting big as you move so what i do when I spawn I get my shot lined up 1st and then move around looking for a victim. Every so often STOP to make sure your still lined up about belly high, shooting from the hip is what your going to do 95% if the time. When I 1st started playing I didnt do this, when the enemy came around the corner I shot over his head most of the time and I took the dirt nap. And NEVER open up in full auto, quick burst are KEY!!
4) Prone Killing is another thing that works great... Say your running around POW map and you see a guy running and gunning at you, Just drop to the ground and fire him up. Man this works SOOOO good when their running and gunning at you their aim is WAY off so when u hit the diry your aim is dead on
This works GREAT in run and gun maps like POW
5) Reloading to often will get you killed!!! This happens to me ALOT.. What I mean is say I fire somone up with 2-5 shots, I still got 20 in my clip so I reload and BAM Im dead because another guy came around the corner while i got the clip in my hand.. Its a habbit I have to break, I mush die atleast 5 times a game because of this... Try to wait unti to know your safe.
These are a few things that I havent seen in other guides that I thought might help somone