Couple tips I think I learned.
1. Make sure the hook angle is right on the popup. I miss more fish on them and attribute it to the hook angle on my rig.
2. Homemade boilies can be made into popups by microwaving them instead of boiling them.
3. You can popup any bait by using foam. I use the foam ladies put between their toes just cut into pieces. I try to fish neutral balanced more but I have a lot of luck popping up a single piece of maize with a small piece of pink foam. Caught my two largest buffs on a neutral balanced blowback rig with maize and foam. I got my foam at Walmart in the beauty section for like $.99
4. I think they may work better on finicky fish, like buffalo. I hear fruity flavors are popular.
5. Rig
http://www.korda.co.uk/rigz/?id=5