Just thought I'd drop a tip here. I'm not sure if the lot of you know this, as I just found it out.
If you aim down the sight of your weapon, this greatly increases your accuracy. However, you won't be able to move as quickly when you're looking down the sight. The Mobility stat of weapons determines your movement speed for this; sub machine guns and shotguns have the best, and light machine guns have the worst. Also, the Steady Aim perk increases your accuracy for whenever you're not aiming down the sight, so this can be useful for the less mobile weapons.
After finding this out, I put "aim down sight" on the C button. I kind of wish that the Nunchuck had three buttons so I could still put crouch/prone on there, but oh well, I don't have to hold that button so it can work as D-pad up. This has definitely helped me improve my game, and now I know how people can shoot me across long distances with seemingly inaccurate weapons. I'm still terrible of course, but now just a little bit less so.