I'm going to do my best to attempt a snapping prefold tutorial, so bear with me :-D There are no patterns I feel I can give you here, because where you place your snaps (or velcro) depends on the size of your baby and how you fold your prefold.
Kamsnaps.com and attach them with a $27 pair of snap pliers which I love. I love Kamsnaps, but I think other places sell snap pliers and snaps as well so you can shop around. All that just to say, you don't have to break the bank getting an $80 snap press. If I'm using velcro, then I'll simply attach squares of hooks to the back closures within the squares, and strips of loops to the front panels--only on the ends--within the squares. With snaps, it's a bit more complicated since you need to measure to make sure that your snaps are all equidistant, but you're basically going to put your studs on the back flaps and your sockets on the front panel.
I also like to add some stud snaps facing the opposite direction so that when my baby gets taller, I can unfold the back flap and continue to use the prefold. When I unfold it, the snaps facing the opposite direction turn away from baby's skin so they never dig in. This also means that I can use the twist fold as another option.
Here's the prefold looking at it from both the back and the front once all the snaps are in their proper places. If you click on the picture, you'll get a bigger view so you can investigate it more if you need to.
Here's the prefold snapped a couple of ways:
1. The Jelly Roll with the back flap unfolded
2. The Twist with the back flap unfolded:
3. Angel Fold with the back flap folded down:
4. Angel Fold with the back flap unfolded for taller babies:
If you want to try something really awesome, you can add elastics to get a tighter fit around the legs and contain the poop better. I do this with the angel fold only. You can either use another diaper to draw the elastic lines or you can fold the diaper the way you would with the angel fold and just draw a line along the fold that curves around the leg. This is what the diaper will look like flat when the elastic is added:
I don't have a picture of the snapped prefold with elastics on Bunny yet because she was napping when I took these pictures, but here it is modeled on her life sized baby doll who is about as big as she was when she was 6-9 months old.