I guess that depends a lot on how booking and patient assignments work at your school.
If it's similar to mine though, the best advice I can give you is to be very hardnosed when it comes to patient management. The first time someone cancels at the last minute or doesn't show up, axe them. Lay out your expectations of them on day one. If you DO decide to give them another chance, tell them "If you cancel again, I will not rebook you." I was too nice and let a few patients take me for a ride, and by the time I decided I'd had enough it was pretty late to be starting from square one again with someone new. But even if you find yourself in that situation, if you drop a patient for a good reason then it's the school's responsibility to find you a new one. If they don't, they can't hold you back for not completing something they didn't give you the opportunity to do.
It's also a good idea to get rid of redundant cases once you have enough of something. Be careful with the perio patients. Recalls can really add up and take a lot of time, so once you have the patients to get you the credits you need, don't take any more.
And finally, if you get credit based on surfaces, look for cases where you can restore, for example, class 4's or class 6's on anterior teeth. At my school these can count for 5 surfaces each (MDBIL), while you'll spend a lot more time on a posterior class 2 and only get 2 or 3 surfaces. (MOD).