are you asking about what kind of perches (diameter, type, etc) to put inside the birds cage, or training perches (like the kind Michael uses in the videos) ?
I am probably going to post a DIY guide on how to build perches that are like the ones you can buy in pet shops sometime in the coming weeks. Instead of costing a fortune though, these are going to cost around a dollar each.
Use bird safe woods for perches, vary the diameter, we have everything from half an inch to 2inch perches in the cage. List of bird safe wood here: http://www.birdsafe.com/woods.htm
Contact me, I have some interesting new perch options available.
If you're purchasing elsewhere, look for diameters between 1/2"-1" for perches. Variety is more important than specific thickness. Provide the variety in the cage and let the bird choose what it likes.
I have had to priviledge of getting the new perch Michael designed. It is absolutely marvelous and my Caique took right to it. At first I had to train him to learn it stepping from a table, now its to the point where he flys 2 feet to get on it. He likes it so much that now he jumps on it expecting a treet without me using the clicker and saying perch. I think he is smarter than expected. Does anyone think I should move on to other tricks or increase the distanes more till he can judge it every time?