the geometry of a road bike makes wheelies very difficult. To be perfectly honest, untill u can ride a wheelie for DAYS on a bmx, you really have no chance of successfully doing them on a road bike. I've ridden trials for a little over a year now, and can get up walls over 3 feet, but cannot sustain standing wheelies on that bike because the geometry is so whacked for that type of riding.
Once you master it on a bike that makes it easy (an urban bike w/ short wheelbase and a really short stem) you can move to doing it on a road bike.
Also, learning on a bike that is easier will help u not to mess up your nice road wheels :_D when you slam them back down from a wheelie.
(oh and gearing is important... you want to be able to apply enough pressure to get the front up, if you can't get it up, you either need to go faster so u can apply more torque, or get new gears)