I like fooling around with my customized thumbnail page grids. The fact that I can print up more of these as I need them without having to go out and buy a pack of them for around $10 USD helps a lot.
These are really not as tight as my usual drawings, but that is the purpose of a thumbnail sketch. It helps you work out bugs in your composition and panel sequences, and you can always go back and redo them.
A partial view of my latest fan art for the DeviantART gallery. Anyone who could remember these characters should recognize them. It was a good old Japanese cartoon series which saw airtime during our youths.