Do your PT. Strength training and endurance running. Get a guide book and essential subjects. Study them and learn your general orders. Read up on Marine Corps history, learn it, know it, live it. Have your recruiters show you how to strip and clean an M16. Get them to teach you rifle manual and other drill movements such as facing movements, saluting, etc. When you get to bootcamp. Be a leader, not a follower. Would you rather be lead by a stranger or would you rather do the leading? Don't be afraid to volunteer, for everything. When your Drill Instructors ask for a body, sound off first, everytime. Most importantly, don't flaunt everything you have learned before Bootcamp. Drill Instructors love a motivated Recruit. Everyone hates a know it all.
One more very important thing. When I was at Parris Island, the plan of the day was posted on a clip board at the quarter deck. It is a breakdown of the training schedule for every training day of recruit training. If this is still SOP, read it on firewatch. Then you will know exactly what you will be doing the next day. Make a note of "Commanders time" This is the fuck with the recruits time between scheduled training events. It's usually no more than 20 minutes long. If you know how long Commanders time is, you will know how long they have to fuck with you until the next event. It helps to know how much time they have to get you on the quarter deck. With this little bit of knowledge, if you keep your shit together, most of the time you can beat the clock.