The first wheelie I did was by accident. At a bank drive-thru, I thought I'd impress some girls in a convertible by doing something stupid on my KLR 650. So I pinned the throttle out of the drive-thru, then realized I couldn't steer. Front wheel had lifted, cool.
Be wary of long wheelies though. My brother, former motorcycle mechanic, says you could mess up crankcase bearings on some bikes by riding out wheelies. Since the engine is tilted back in a wheelie, some bearings might not be oiled properly and sieze or wear out. Sounds iffy, but I've never heard otherwise. Trials and motocross riders seem to do it all the time, but maybe 2 cycle engines aren't as affected.
Oh, and don't try to impress chicks on a KLR 650.
Girls aren't impressed by dual-purpose bikes.