1. Getting into a character's head and hearing their voice as I type.
2. We watched Trinity Theatre Club's Summer Lightning, an adaptation by Giles Havergal of a PG Wodehouse novel. The script (and the scenery) acknowledge the story's roots -- characters often break off to describe themselves in Wodehouseian terms and the scenery has a curiously painted paper look to it.
3. Looking at a huge project and feeling that it can be done, and knowing you have a friend to help you out.