Practise on a dirt bike on the dirt. It's a) less painful when you flip it, and b) does less damage to the bike.

Best wheelie flip I ever did was at the Brit GP back on 90 or 91. Drunk as a skunk, just wearing shorts and trainers, and top quality Arai hairstyle. Saw some mates hooning on an ancient Yam YZ490 so I stole it and was just hooking top gear on the back wheel and over it went.

Carried on playing the fool for the rest of the night.

The next day (sober) it hurt so much I couldn't move. I'd pretty much ground my back away to the bone. Oh what fun.

Since that day I've never lofted the wheel without just giving the rear brake a tap before I give it the berries.

And since that day I've managed to flip my NSR250 and a honda step thru'.