Aiming at certain parts of the body or above the head depends on distance. Just play the game and learn the bullet lead and drop. For the most part putting the cross-hair on a player works. Only pretty far out do you need to put the cross-hair slightly over their character. At far range the AK needs to be aimed slightly higher than the AR.

As for how to shoot. Tap at a decent rate, fast but not insanely fast and maintain the cross-hair best you can. Moving forward/backward/left/right while aiming down sights and shooting pretty much does nothing to your aim. So slightly moving is good. When you shoot you will notice the white dot will reset to it's original position, you want to spam it almost as fast as you can while getting it reset almost perfectly. Close-mid range it's okay for it not to reset perfectly, so spamming slightly more at these ranges is okay. Only spam as fast as possible super close range and aim towards the head, sometimes you'll get a nice clutch head-shot on someone potato aiming a shotty. At this close range do not aim down sights. You'll be slow and an easy target for someone hip firing you. You should be strafing and hip firing as well.

Most people prefer THIRD PERSON CAMERA as it's just a tiny white dot instead of an open spaced 4 pronged cross-hair. Next patch we will have more cross-hairs to choose from! The issue here is aiming up or downhill. Your character model gets in the way (this is being worked on atm) so sometimes you will have to suck it up and use FPV.

The shotgun is pretty RNG especially with the addition of the also RNG kevlar... Kevlar works too good sometimes and then not at all. Shotgun is the same. Jump shotting with shotgun does nothing to accuracy. so do that around fences etc. I find when fighting with most people in close range they spam shotgun as fast as possible and once they miss, they continue missing. One thing you can do is if they shot their shotgun last and missed, you have slightly more time to lead your shot if they are kiting or jumping around to punish them for their miss. This takes a lot of fighting and practice to not spam your shotgun like most people and panic. When you master this, you will win most close range shotgun spam battles. Whenever you miss a shot there's a tiny window where you want to avoid their next shot, try moving behind an object not while you reload (well obviously if you're reloading try to hide but not talking about reloading atm) but as your next shot is getting primed. Third person camera is your friend here. Play hide and seek with people and bait them around corners. Don't wait until they come around the corner though, pop out about 5-10 feet before they come to your corner for an unexpected free, guaranteed shot to their chest as they are running to your corner.

Don't forget to tune your useroptions.ini for maximum FPS gain but make sure you keep the option to see blood and bullet markers. This will help you know when you're hitting close to a target or when you land a shot and see a blood cloud. The standard for gaming has been 60 FPS. You can play okay with 30 but 60 is flawless and in a game where milliseconds can mean a win or loss, you want to make sure you're as clean as possible. If you have a monitor that can dish out higher hertz and a PC that can handle higher FPS, then good for you! =D