Very similar to the above suggestion, but I found it easier to hold down the left stick the whole time and just tap A until the wheel lifted then stop tapping, rinse and repeat until you got the achievement.
Also I found it easier to do this while you were riding to places instead of just riding to do the achievement cause then it gets really boring.
Edit: you can check how many wheelies you have done here. Stats>general>Bikes>Wheelies (thanks to adventurer90)