Aaah,brings me back. I dod my clinical preceptorship in L&D almost 2 years ago. I just recently accepted a job on that very same unit!
Things move very quickly. Remember to jump in there and help out wherever you can. There will probably be alot you don't know. But you can always hold a leg during pushing,get water, blankets, support for the parents! I would sit down with my nurse after the delivery (when there was time to talk) and ask my questions. Why did you do this? What should I tell the mother if this happens? What should I do if this happens again? etc..
My preceptor would try to let me feel cervixes on our epidural moms, if they were willing. That way they could not feel what I was doing, since I really didn't know what I was doing!
Have fun and ask lots of questions, show your interest. Make a point to meet the manager! That way she'll remember you if you have a chance to apply for a position.