You could probably jump right in. First off go get a club checkout in a 172 or whatever airplane you will use if you haven't been flying GA, then go buzz around a little. You don't want to be rusty the first time with a student.
After that, you could probably review the basic 91 stuff and then do heavy academic prep for each lesson in advance.
One thing you would want want specific airborne practice for would be commercial maneuvers. Either try it on your own or get a CFI to help you out. Same would apply for any ME engine-out stuff.
You could also devise a refresher course with a CFI, but that might be expensive overkill, depends on you though.