Establish Rules and Expectations
A sitter also needs to know what you expect from her. Do you need her to feed, bathe, or put the kids to bed? Tell her a little bit about your kids, including what they're allowed (or not allowed) to eat, whether it's acceptable if they watch television, when they should go to sleep, if they have any bedtime rituals, and so on. One of my friends even leaves detailed lists of what her kids like to do and what distractions to try if her baby cries.