Usually you get to pick your schedule or work hrs.
There are 8, 10, and 12 hrs shifts.
You can choose to work a full week, certain days during the week or the weekend. I personally like the weekend because of baylor pay. That means I work 24 hrs during the weekend (12 hrs Sat and 12 hrs Sun), and I get paid for 36 hrs.
Hope that helps!
***Forgot to mention:
There's also graveyard shift (night shift) of 10 or 12 hrs.
It all depends on where you work hospital/clinic and the flexibility of your supervisor. My hospital doesn't do on calls or weekend rotation.