For your sub-I. Get netter and Koval. In addition work hard and volunteer for late cases. Your can do attitude will be appreciated. Also, do not worry about every little detail. You are a student and are not expected to know everything. If you answer a question wrong do not sweat it. Our attendings often want an interesting person who can bring levity to the OR at 3AM, not discuss the recurrent branch of the radial nerve.
Things you should know in detail as a SUBI are
1. Classification of open fractures. You will be pimped on an open fx with dirt, barnyard exposure and are axpected to answer give Kefzol, Tet, gent AND PENICILLIN.
2. The basic exposure for the case you are doing
3. How to suture
4. What fractures require immediate fixation (up to debate). Talar neck, etc
Volunteer to perform a talk. This will showcase your PS skills.
Best of luck