This is my personal favorite to use right now. To do a jellyroll, you lay the prefold out flat and roll in the edges so the front of the diaper gets smaller but the back gets "wings" to use to snappi or pin around baby. The roll makes a barrier between the inside of the diaper and the outside, which is one of the things I really like about it. I've also noticed that I can get a really good, tight fit with this fold.
One downside to this one is the time involved, especially if your baby is squirmy. I've found that I can get the roll started before even trying to change my son's diaper and then finish it up on him.
2. Angelwing Fold
This was a fold I used a lot in the infant prefolds. It was so easy to do, even for a newbie like me! Here's how it works. You lay the prefold flat, the long way, so that the top of the diaper is under the small of the baby's back. Then you fold in the remaining fabric similar to the trifold, pull it up through the baby's legs and snappi (or pin).
I like this one because there isn't a lot of prep work to make it work well on any age. And I also found it to be the easiest fold (aside from the trifold). Plus, this one is really great if your baby is almost out of their prefold as you can often still squeeze the pins in place at the corners.
The only drawback I've found is that sometimes you have to fold excess fabric down in front, which leads to bulkiness at the front. You can solve this problem by moving the fold to the back if it truly bothers you.
There you have it! My four favorite prefold folds! There are definitely other folds and variations of them all, but this is how I do them. I hope it was helpful.