Amen to CSAT standards.
Also look at everything Kyle Lamb has put out.
Work hard on reloads, malfunction clearing, getting in and out of positions, using cover as said above, moving properly under fire (high crawl, low crawl, 3-5 second rush, PRACTICE these, wearing what you'd be fighting in), work multiple targets at various distances, partially obscure targets (bad guys use cover too!), etc,, off too of my head.
And shooting standardized drills periodically, like El Diablo, El Presidente, 15 Seconds Of Fury, MTS 9 Shot Drill, etc., will show you areas you need to be working on.