If I were to go back to the last summer, I'd definitely look over the materials beforehand. I have been in the serious disadvantage because I've never taken anything other than premed requirements. You guys have a lot of time before class starts so why not just invest 3 hours per day 5 days per week? I promise you, it will help you a lot. Even though I'll be spending most of my time this summer doing research (8am-5pm weekday job), I plan to use my night time and weekends for previewing 2nd year materials and preparing for step 1. Of course I will still enjoy weekends and keep working out during weekdays, which is good enough for me.