We have a PT after-school nanny for two elementary school kids, so ours might be different than you would have for a small child. We also use occassional evening sitters, and these rules are posted along with general household information (e.g. location of first aid supplies) on the fridge. Some of them are posted so that my parents (occassional sitters during school breaks) can see them -- this was sort of a passive/aggressive way of making sure they realized our household rules were different than their's were when I was a child.
Our basic guidelines for nanny/sitter (in the order I remember them):
Children are to be respected above all else.
Children must NEVER be struck or subjected to ANY physical discipline, shamed, or humiliated. Sitter/nanny may ask children to play separately/apart if sibling interaction is not positive.
DD must be in carseat, but outings are encouraged. Advanced permission is not required.
Sitter/nanny must have cell phone available at all times when out of the house.
Sitter/nanny must ask permission before including others in sitting or outings. Permission will generally be granted.
Children may not be left alone with another person (any gender) or driven by another unless background check completed and advance permission obtained.
Children may eat what/when/where they please -- they know what few things aren't allowed. Nanny/sitter may do the same.
Use of alcohol or use street drugs when caring for children will not be tolerated.
Nanny/sitter must be within visual range when children are using the pool
Nanny/sitter may permit or decline playdates with neighborhood children
Nanny/sitter is expected to ensure children get to preplanned activities on time and with appropriate gear