Look into order of merit for UPT selection. A substantial portion of the OM is commander's ranking. That's the only place those other activities to potentially come into play.
If you're still in high school, choose a few extra curriculars that you will stick with and excel at. If you're in college, your time is best spent on not being a reliable cadet, having a good PFT score, and having a decent (3.0 GPA). It's a balance, though. Don't wholly sacrifice one category for another. I saw a number of guys in college try to be involved in everything the detachment did only to lose sight of the other categories and get kicked out of ROTC for a bad GPA. On the other end of the spectrum, "ghost cadets" also didn't fare well.