For me there are these areas that are always included when I brief a helper:
- job expectations and duties (what's her job and what isn't plus specifics on how I expect certain things to be done)
- values and non-negotiables (cleanliness esp. when she's handling the baby, values like honesty --- it's ok to make mistakes as long as she tells us and doesn't try to hide it)
- compensation and benefits
- schedule/routine
- safety warnings (don't talk to strangers in the park, etc)
then we do a tour around the house and I teach her how to use baby appliances like the food warmer, and what products to use for baby's laundry, toys, etc.