These two items may seem obvious for many, but I discovered them first hand a few weeks ago when I first integrated my first march pump into my set up.
1. There is alot of discussion about the orientation of your pump head. From my experience, a vertical orientation is better (with the outlet at the top). I was told this by my LHBS owner as well as several posts on here, but ultimately found it was true under my own experiments.
2. This one may seem really stupid... but, the pump route must be an open circuit at least to start with. The main use of my pump is to recirculate wort back into the kettle and across the IC I use. Because the return is under the surface of the wort, air is trap initially by the pump and hosing. It didn't take me long to realize my return needed to be above the surface of the wort (and free flowing) to allow that air to purge the line.
Long story short: whatever your set-up is, make it easy for the air to be pushed through the system in front of the wort and you should avoid cavitation as much as possible.
Hope it helps!