From what I've read, the average club tennis player in the US that plays 2-3 times per week and has been playing for 5+ years is usually about 3.5. So there is your middle of the spectrum, average rating to judge yourself against.
How long have you played tennis?
How did you learn?
What is your competitive background?
What are your goals (ie, tournament play, league play, or pure recreational play)?
If you are very inexperienced, I think you should probably self rate at 3.0 and play tournaments at that level. I don't think there are many NTRP tournaments that have draws lower than 3.0, so that is the entry point for most beginning tournament players. If your goal is to play USTA league and there is a 2.5 level team in your area, you might want to self rate there. You can always play up (2.5 playing in 3.0 tournaments), but you can not play down a classification level.
If 3.0 tournaments turn out to be too easy for you, generally there are many very good and experienced players in 3.5 tournaments - and as I said, you can always play up a classification. The guys that win at the 3.5 level are usually young dudes on the way up or older folks that used to play at a higher level but have lost speed and strength (but still know how to put points together and win). In both 3.0 and 3.5 tournaments, you will run into a lot of hackers and pushers, which are guys that have very unconventional looking strokes and just get the ball back in play. A lot of players at this level that have been developing classic strokes will lose to these type of players and want to commit suicide, but if you stick with it long enough, commit to your game, and learn how to put points together, you will eventually raise your level to 4.0+.
4.0 tournament players usually have good overall strokes and have something of a weapon (like a good forehand or serve), but also still have a weak point in their game that can be exploited with enough consistancy or pace. There are hackers and pushers at this level, but they generally have more conventional strokes and really know how to strategize. The same could be said for 4.5 level, except those players generally hit a little harder, make less errors, and have a more polished overall game. Most 4.5 players have a high school or college (JC or small college, or fringe major college years ago) background and have played competitively for many years. 5.0+ guys are usually big hitters in the 19-50 age range that pound the ball and look like a professional to the average person.
