Practice. That's the big thing.
From a technical perspective, make sure the workpiece is well secured. It is hard to rivet if the assembly is dancing around.
Also, put a piece of masking tape (the blue painter's tape is good) over the rivet heads before you drive them. That seems to add some friction and keep the rivet set from bouncing around as much.
And use a heavy bucking bar. It helps.
But mostly practice.
Another hint is to make sure you're pressing against the part with the gun the entire time. Don't release the trigger and simultaneously reduce pressure against the part.
Did I mention practice? Honestly, I was all the way through the empennage before I could drive a row of 1/8" button head rivets without needing to drill several out.