Here are a couple of my tips:
1. Try to stay in buildings and covered as much as possible.
2. If your a sniper, either have someone guarding your rear or get claymores.
3. DON'T run around spraying bullets, your just gonna get killed.
4. The best weapon for you is the one that is portable, does enough damage, and that you are accurate with.
My opinion of weaponry and perks:
Best perk= Overkill
Best Sniper= Dragunov
Best Assault Rifle= M16 with an ACOG
Best SMG= P90 with dot sight
Best LMG= SAW with dot sight
Best Shotgun: I don't give a crap 'bout shotguns.
The 50. cal WOULD be my fav but it does the same damage as an R700, which is outrageous.(considering if you got in the arm with a 50 in real life, your arm would immediately be blown off)
Just a question for those prestige out there, is prestige really worth it?