Should someone join the ROTC in college and make the best grades possible, etc?
Or should you enlist right after high school?
What is the ideal career path for someone who wants to be a helicopter pilot in the Navy or Army or Marines?
For Army, look into the Warrant Officer flight program. You need a high school diploma.
To fly in any other branch you'll need a college degree and good grades.
I'm not demeaning the Army program, it is a very good program. Flying a helicopter or airplane really isn't that hard. Before WWII and into WWII Marine enlisted flew aircraft. I think enlisted pilots is a good idea.