This sounds very simplistic but all you have to do is make sure the front is high enough before you change. IE nearly vertical. This is quite buttock clenching initially, but what you have to remember is that even a slight amount of engine braking will fling the front end back down so there is little chance of flipping it. First gear is a bit viscious so I normally lift it in second which softens the power delivery and engine braking. You just have to keep asking yourself "what is stopping me lifting the front higher" ? The higher you get the front the less power and acceleration you need to keep it up. Eventually you will be able to momentarily back off to change gear and then get back on the power before the front drops too low.
There are a few basic rules to wheelies:
1.) The front can always go higher than you think. What you think is absolutely vertical will probably only be 45 degrees when you see yourself on video.
2.) Be very very smooooth with the thottle.
3.) Dont do it if you are not prepared for the consequences of looping it. (Yes that is where the name Loopy came from !)
If like me you do get the bug badly, get yourself a dirt bike and you can practice off road where it tends not to hurt as much. Pulling a balanced monster wheelie still makes me howl with laughter inside my helmet and I have been doing it for 30 years !
