Memorize your general orders and rank insignia before going. Keep your eyes and ears open, your mouth shut and take care of the other recruits around you.
What Paul said and run,run,run and run some more and it wouldn't hurt to get some PRAC ( Marine Corps knowledge ) down. You're going to need to memorize and ingrain things such as who was the 13th Commandant of the Marine Corps or what Marine has been awarded 5 Navy crosses? start now, fail to plan plan to fail.
.. I'll probably need it.. Going from civilian life to the marines will be a shell shocker for me
Remember to capitalize the M when typing/spelling Marine(s) or Corps