This is my rifle, this is my gun. This is for fighting and this is for fun.
Dry fire. Dry fire lots. Do a lot of reload drills. Then dry fire some more. Practice tap racking--or SPORTS (I prefer tap-rack). Practice stripping off a fucked up round off the corner of your magwell. Practice Double feeds. Practice transitions. Practice slicing the pie. Practice....Being a Mall Ninja.
W/ respect to use--unless you live in a hilly area as seen in Afghanistan, most rifle combat takes place within 100 yards, so keep that in mind.