Well, a typical American CHR station is typically going to be very current- and recurrent-based, with only occasional gold categories. You're going to want something that allows you to work in new titles as well as titles that you only want to play at night -- although sometimes, a nights-only current category may not be filled with any titles. Right now there is kind of a lull in the nights-only type of music on CHR, in my opinion.
So a CHR category layout might go like this:
- hottest power currents
- secondary currents
- tertiary currents (songs that are declining but not ready to be enshrined in your recurrent rotation)
- nights only currents (may or may not be used, depending on your need)
- new music
- power recurrents
- power gold
- secondary (filler) gold
That would probably be where I'd start. It's all about determining the need for your format, and splitting things down to more specifics from there. With a format like an AC you're obviously going to have fewer current categories and more gold categories. In an AC you may only have 2 or 3 current and recurrent categories, then 8 or 9 gold categories. With CHR it's the opposite. With Top 40 radio your audience wants to hear fresh, hit music, so the categories should be based mostly around the popularity of your titles and filled appropriately, so that songs in your secondary category are getting fewer spins than your hot currents, for example.