When I turn 18 I am going to join the USMC. I am currently 15, so what can I do (Physically) to prepare myself for basic training? Thanks.

steroids.

ok im kidding kid.  do a lot of aerobics and strength training. eat well.  

Simple: do the same thing they do on the USMC PFT Test for a 1st Class rating.

80 situps in 2 minutes.
14 or more pullups w/o raising your knees.
Run 3 miles in 18-20 minutes.

Keep in mind that you may not be able to do these right off the bat but it gives you **goals** to shoot for.

Also, learn to clean your room & do ALL your family's dishes until both are squeeky clean.

Go watch the first half of "Full Metal Jacket".

Learn to shoot an AR-15, take it apart & clean the shit out of it.

Good luck.

What about push-ups? Is that only Army? Should I try to build strength AND bulk, or just strength? Thanks.

The best thing to do is maintain some kind of healthy lifestyle and play sports.  Don't worry about getting "in shape" ...The Corps will take care of that.

Relax and enjoy your youth.

watch one of the specials on Discovery or TLC, push ups are a must [;)]

Pushups is Army and Navy..not sure about Air Farce.

For somebody your age I would highly reccomend avoiding the weightroom.  The most resistance training you need is your own body weight...

Depening on your body type and its state of development its easy to get injured by pushing yourself in the gym on weights.  Also, in my experience, most recruits that have large amounts of muscle mass can't maintain it during boot camp because of the nature of the diet and the type of physical training.

Again...you are 15yrs old and 3 years away from having to go through the transformation from civvy to Marine.  Relax...don't get fat...stay out of trouble...

Be active...play sports...  The only way you would have any trouble with boot camp is if you are overweight, can't run a sustained pace for at least a mile.  If I would pick a single excercise to make sure you could do well it would be the pullups.  Its hard to get good upper body strength quickly...abs and run improve much faster than upper body strength.

Don't go gettin' a girl pregnant.