I'm PT in Riverside Co. How it works out here and I'm sure its pretty universal throughout AMR is you have to work 3 shifts a month minimum. Its no set schedule, and pretty much how it works for me is two ways:
Option A: I log onto telestaff and put in for shifts or go available for set days. When you put in for a shift ex. 0500-1700 you're only going available for that select shift and hours. When you go available for set days for ex. going available for 24 hours you pretty much cover every shift.
Option B: If you rock the pagers like we do, the supervisors page out open shifts daily for EMT's and/or medic's. To pick those shifts up (and they can be anything 0700-1900, 1700-0500, you get the idea) all you have to do is call the supervisor to pick it up.
All in all in my division its pretty easy to meet the 3 shift a month requirement. A lot of the time I work just as much if not more hours then the full time employees. I just got off a lovely six day stretch. The only negative thing about PT is theres no guarantee that you're going to work 3-4 shifts next week. Next month I could only work 4 shifts for the whole month. But the benefits outweigh the negatives IMO. I don't have to worry about taking days off for vacation, I work the first 3 days in the month and I can take the rest of the month off if I want to. Also you're flexible if you're in or going to start school.