1. Get a good scope. Never choose that dumb ol' Soviet Union standard issue. With a bad scope, you'll be shooting like this when you're too zoomed in and your gun releases to much smoke.

(You won't be able to see a thing and the bot will most likely kill ya)
2. Go for the Specialist class. Very decent and overall good scenario guns.
3. If the Specialist class isn't available, go for Support Class and use the M249. I go on to every ASH server and someone is using that class and that gun

Now against a human sniper or rifleman... the Support stands no chance

4. Never ever ever buy the shotguns. They're terrible if you a) in an open map and b) if you're stuck being the last human alive. Not the best of weapons to take out snipers >.>
5. Grenades are your friend.
6. Don't pull a SONOR and start C4'ing the whole place sky high :p
7. PVP is much harder than you think. Playing against humans is way different than bots.
8. Try out the other classes. You will come across servers where the 'best' classes are already taken. Get used to the others.
-Mandalor