first of all, if you had been a sportsperson yourself it will become very easy to understand the rules of sports which are required while writing any article. but if you have not played then also it is ok.
the ideal way is to first complete a journalism course from any university and then apply to certain newspapers or wires. i know about delhi --it has times school of journalism which gives placement also. like that there are other institutes as well.
To become a sports journalist, you need to be updated with all the sports news by watching news channels and also read a lot of newspapers and current affairs magazines. Its not that tough!
Try reading books on rules of sports fr example how football is played, how many players are there and what are the rules of the game.
If you do not know the techniques and rules you will be in trouble and sports journalism will become really tough.
If you now beforehand and have a flair for writing then you could a sports journalist even without doing a course. This happened with me -- I started as an intern with a newspaper and then they employed me. I am not saying i knew eveything but with time i did learn the desk wor like how to mae newspaper pages as well. By covering events i got to know more about players and thats how it went on.
But don't think it was easy for me. I used to read a lot of newspapers and watch news. Then i started writing letters to the editor almost everyday. And when i went to the same newspaper for an internship, i was excited as people there knew me by my name -- the same girl who used to write letters to the editor everyday.
H\Journalism has two areas -- desk work and reporting. For reporting you have to do what i told above. But if you want to sit in office and edit stories or make pages then you need to know how to do it. You have to learn Quark express for that. you can get a Cd at home or search for sites online to download the application. If you know both desk and reporting work it will be very easy for you as generally sports journalists are required to do both.
hope this information helped you!