No problem
Yup, knowing the maps really well is probably the most important thing for any multi player FPS game.
Few other tips:
Recon is a superb class to use, the ghille suit is a huge advantage especially on the jungle maps, it really does confuse some enemies as to if you are on their team or not when up close (on hardcore, thanks to it, I have been able to go on many knifing streaks that would not have been possible if I was playing as some other class
), combined with the motion balls and either the SVU or vss (this is a tricky weapon to use, fire in very short bursts as the bullet spread is crazy, sometimes the hit reg. seems completely of with that gun compared to other guns
), you are a silent but deadly soldier. The GOL is the best long range sniper imo, extremely accurate and no scope sway.
Engineer's best weapon from my experience is the uzi, crazy good at medium-long range. 9a-91 is also really good.
IIRC with the medic, I used the MG 3 a lot
For assault, the M416 and M16 are the best. F2000 is a great weapon if you are often in close range (which with rush mode is quite often
if you are an aggressive player). The noob tube is essential too!
Best Pistol imo is the M9 (use to be the M1911)
As for perks, can only remember using magnum bullets and for vehicles extra armour or smoke (vital for the heli, this is flares)
People like to use mines/C4 in this game a lot so always keep an eye on the ground (especially where there are holes and the ground is black or has a tree etc. covering it)
all in all, I would say eng. and recon are the best classes to use. But if you want loads of points then the medic, you are essentially Jesus and Rambo in one!
And if you really want to rake in the kills, get a good pilot and practice with the mini gun in the blackhawk (use the left mini gun as it is harder for people to shoot the pilot out then), no joke, people think the apache gunner seat is good, even OP at times, it isn't even close to a good mini gunner
Just need to know/learn where abouts the bullets impact etc. Some people use blue-tac (since in hc you don't have the hit/aim markers) but I personally prefer not to.
EDIT:
The UAV is extremely useful when pushing forward especially with the smoke attachment. But make sure you always keep and eye on "yourself" as you are guaranteed to get some base raper noob, tbh, try to find a server where people get kicked/banned for base raping (at least for the attackers on rush mode) as it can ruin the game imo and unfortunately it happened a lot during my time of playing this (at least until I found good servers)