If you play USTA or USA, as they call it now, you will get a computer rating. Your computer rating is based on who you played during the season and how you did. It also compares who you played with everyone they played, etc, etc. Some tournament play counts toward your computer rating as well. If you well enough you will get moved up by the computer analysis. I don't know how the majority of folks on this board determine their rating or level. If you have a computer rating, tha's the level. I always question the response " I'm playing at a 4.0 or 4.5 level". None of my business, though.
I have found that the talent level for any rating is very, very broad and can cause some doubt as to the validity ot the system. All in all, it seems to work most of the time.
If there are no USTA leagues in your area, start one. Or find out where the nearest one is to you and get involved.