I bring a towel to add as padding. Lessens the recoil and that helps. Also, and I can't stress this enough, use good ear protection. I use plugs and muffs and just cutting down on the noise helps. Also good eye protection, preferrably glasses that wrap around your eyes. Sometimes it's the feel of the muzzle blast and noise that will worsen your flinch.

Then, try not to jerk the trigger, just slowly squeeze it as the crosshairs float around the target's center. Like they said, when the gun goes off you want it to be a suprise and that's where a lighter trigger pull and good trigger will help. I want to be suprised every time the trigger breaks and that usually makes me more accurate.