Hi,
Well, first off I will tell you that leaving a bird flighted is doable if you are careful and take extra steps to keep the bird safe. Having their wings is healthy both physically and mentally for the bird. If you can't leave the bird flighted then clipping is the way to go.
First of all, never leave the first one or two feathers intact if you are going to clip. That is called a show clip and it is done purely for aesthetic reasons. It is actually dangerous for the bird as the feathers that are left jut out and there is a space where the other wings are clipped. This allows the outer to feathers to easily get caught in cage bars or toys etc. Also, the feathers lose the support of the other feathers and can more easily break.
Different birds require a different amount of feathers to be cut. Never go past seven. For most birds 4 or 5 will suffice. For a small bird like a budgie you may have to go to 6 or 7 but always start out with less. You can always cut more if you need to but you can't put them back if you cut too much. I'd start with 4 on a budgie and then see how he does. He should glide downward towards the ground. He should still be able to fly a bit as well. The idea is that he can't get any lift. If a bird falls immediately to the ground then they are clipped too severely.
Another important factor is you must allow a baby bird to fully fledge before clipping their wings. That means they should be allowed plenty of time to learn to fly, at least a week or so. It is extremely important for their mental and physical development that they be allowed to fledge.
Here is an article that shows how to clip.
http://www.birdsnways.com/wisdom/ww19eii.htmHope this has helped.
