Congratulations! I've been working in OB (high-risk antepartum, postpartum, newborn nursery) for nearly a year... I have a few suggestions:
1. Remember your teaching, and know it well. Know how to teach about breastfeeding/bottle feeding, how to pump, danger signs (when the patient should call for you or the MD), diaper changing, cord care, circumcision care, involution, perineal care, etc. I usually make it a point to try to teach about these things as I go along in my head-to-toe assessments on mom and baby... it helps me not to miss anything.
2. This ties into #1... study up on your postpartum and newborn emergencies. On your first day, ask your preceptor where the unit's emergency supplies are, and ask what the policy is for emergencies on the unit. MDs will see you in uniform now and, if there is an emergency, possibly expect you to jump in immediately and know what to do.