If you want to get good at hipshooting (i.e. shooting without use of the iron sights) then there's only a couple of things to remember. Firstly, bullets go where the barrel of your gun is pointing. Since you're holding the gun slightly across your body, you tend to shoot a little to the left. The length of the barrel plays a big part here, as shorter guns have less "left-lean". That means that carbines and smgs are much easier to use from the hip than say, the Kar98.
Next, don't try it from long range - not unless you want to die. Hipshooting is only for pointblank "oh noes I'm screwed!" situations.
Lastly, if you have a semi or full auto, don't panic and empty the whole clip. The more you fire, the more the recoil will throw you off target. What usually happens (unless you've got very good control) is you run out of bullets and the other bloke calmly walks up and clubs you in the face. Instead, fire in bursts, long or short, it doesn't matter. Just make sure that if you aren't hitting him, then you stop and re-aim, otherwise you'll be back in the respawn queue.
