I do not work for PDT, but this could not hurt...
1. Look over FOM
2. Mem itmes must be memorized
3. Limitations
4. Profiles/Call-outs

If you have those down prior to ground school I think you should do fine. Systems are comlicated, and it is probably better if you just learn them in class the ways PDT wants you to know them. After they are taught that is when you should review, review and review some more.
Good luck!