Hard work, and lots and lots and lots and lots of luck!
(Did I mention lots of luck?)
There is no magic bullet.
You are smart to begin early. Get to some Camps that will give you exposure to the NBA system. I recommend Coast to Coast Referee School. It is run by some of the best in the business, and Ed Rush and Joe Borgia usually attend.
Derek Stafford has a camp, Ronnie Nunn has one in Texas.
Most of all be patient!!!! Some have made it fairly quickly, but most have had to endure, endure, endure.
After many years, I was fortunate to work the WNBA last season. Unfortunately, due to league contraction and other factors, I was not retained for this year. But I am going to try and get back there if I can. I also was fortunate to work the CBA this year. Great talent, and TWO MAN CREWS!
You have to work your butt off, but if you can ref Pro ball with a two man crew, you can ref anywhere.
If you have anymore specific questions, feel free to e-mail me. Eli Roe sometimes checks in on the board.
Eli works the WNBA, NBDL, and worked several Pre-season NBA games. Great guy, and one of the reasons I will miss being on the WNBA staff.
He can probably provide more insight.
Good luck.
Drake M.