The first thing you want to do is post photos wherever you can, and ask for critique and advice. I like that you have the right attitude. My first big time camera (other than film) was a 5D Mark II with the 24-105L lens and I practiced, practiced, practiced. Luckily one of my best friends is a photojournalist and I learned tons from him.
If you ever do want to go professionally into sports, that takes even more luck. I had contacts from when I was a cross country/track runner at AU. Again, luckily they knew I was a photographer and so I got a sideline pass from them one year (I asked for one, they didn't offer it outright). I then bit the bullet and produced a few 8 x 10's from each of the sports to give them (they cost about $1.65-$1.75 to print) for free and then they came back and wanted me to do more. Now my job is to shoot all sports and produce 8 x 10's each season for the sports hallway and to provide discs of each game so that the university can send to newspapers, newsletters, programs, other websites, etc. Interestingly, the local newspaper has the contract to put up the "update photo" right after each game/event to the AU sports website, but that's usually just a single photo that scrolls across as the headlines scroll across. Anyways, once you start doing it professionally, others find out and have you cover events. I went from just doing AU, to the NCAC conference, GLIAC conference, News Journal, and Telegraph-Forum. This weekend, I'll be doing the NCAA Division II Midwest Region for Women's Basketball. I have more stuff than I can manage at times.
Keep up a great attitude, be ambitious, put your work out there and if you see an opportunity, take it. For instance, small colleges and universities will often let you shoot sports with a pass in exchange for a disc of your photos. You may not get paid at the beginning, but if you do good work, trust me, you'll get the work.
Use flickr, use us on this website, use anyone that will help you. I've learned a ton on here and a lot of people on here love helping/teaching others.