Re: How to be a tennis fan?
You should start by finding a tennis player you can relate to.
If you are lucky go with Djokovic, if you have perennial wedgies go with Nadal, if you are the undisputed GOAT go with Federer, if you are British go with Ward and if you think you are important, go with Roddick.
Follow your chosen player's activities and get excited when he plays, happy when he wins, and disappointed when he loses.
At this point you would be classified as a fan.