I'll give stuff a shot in Omnibus if I've heard good things about it (for example Bendis/Brubaker Daredevil/Cap). I rarely do this in any other format for some reason. I like knowing I'll be able to sink my teeth into a book. I'm happy to walk away once the core run is completed. I buy almost every Omnibus, largely because I've found some gems that way and know I can sell whatever I don't enjoy without taking a hit.

I'll buy certain titles only in OHC (for example the Bendis Avengers books). These are titles that if they stopped being available in OHC I would be fine walking away. I enjoy reading New Avengers, but if the line switched to MPC or trade only I'd just stop reading them.

I sometimes try stuff out as Masterworks that I'd never try otherwise (for example, Inhumans and Jungle Adventures).

I buy a few long-running titles as trade paperbacks and custom bind them every four or five collections (for example Hellblazer and the two core X-Men books).

I buy every Masterwork and OHC release for X-Men. This is my only essential purchase. If Marvel wants a guaranteed sale from me every month, they'll have one of these in their solicits.

I buy a few finite series in hardcover; Preacher, Swamp Thing and the Absolute editions of LoEG and Sandman. When they're done, I won't have to spend that money anymore.