Brendan Fitzgerald makes excellent points here, but I'll go at it from a different perspective. One way to get noticed is to do some related hobby in addition to your day job. For me, that's the "In The Gate" podcast. I don't get paid to do this podcast - my day job is as a TV features producer, a job that will get me noticed by absolutely nobody. I could do this job for 50 years without ever receiving a promotion or being noticed by anyone at this network, another network or a boutique third-party production house.
For many reasons that I would rather not delineate here, I decided in 2012 to start hosting/producing the "In The Gate" podcast as a hobby. Now, horse racing is a very niche sport, so even my best work is not likely to get noticed by the masses, but it has gotten me noticed by many within the racing industry. I've had the creative freedom to do all sorts of things with this "hobby" that I would never have gotten to do with my day job, where my assignments are at someone else's whim.
That creativity and freedom a) allows you to find your voice, not the voice someone else wants you to have b) meet a whole new group of people you'd likely not have met otherwise. Depending on what that hobby is and where it takes you, you never know who you will meet and what you'll see as you go down that path.
Hope that helps. Best of luck moving forward!
The best way to make it big is to really be in love with the work. If you truly want to cover sports, you need to work at it wherever and whenever you can. You need to be willing to move just about anywhere (I started in Casper, Wyoming) and do the best job you can. If your thought is about making it big the whole time, you'll spend more time wishing you had a bigger job and really take away from helping yourself.
If you're more focused on being famous and having a major job, but don't love the day-to-day of actually reporting sports, looking for stories, going beyond the games... then you will fall out of love with the profession pretty quickly.
Work on a demo reel, look for entry level on-air jobs (in small markets from coast to coast) and focus on what you can do to get better each day, each week. It will add up to huge improvements in a shorter amount of time than you think. What may seem to be 10-20 years away can be accomplished in 3-5 if you have the right attitude and mindset toward improving and learning the business.
Get a job somewhere as a sports broadcaster and work at pefecting your craft until you are doing network quality work. Work hard, rememebr it takes 10,000 hours of work to master anything. This may mean doing it Bismark, ND and moving up. Find mentors to learn from, or at least look at the people in the industry who are successful and study what they do. Finally market yourself. Put yourself out there. Don't let rejection stop you. You will get lots of it. A lot of things in life are not what you know, but who you know. So always be introducing yourself to people, but also too... You are are in or endeavoring to enter a very small industry. Someone always knows someone who knows someone. Your work ethic and reputation will proceed you. Try to work at being an exceptional person among your peers.
If you don't have a job yet, then practice making tapes as a sports broadcaster. Watch games on TV and make your own color commentary. Know the basics of what it takes to do the job. Don't think for a second those guys on ESPN didn't have to pick up a camera camera and go cover a high school or college game in a lesser market, and put together a story on a deadline. Theres a lot of work and time that goes into achieving anything.
Start small, always look for ways to refine your skills, learn from others and seek out constructive feedback. Your career in the sports media industry, or any field for that matter, is a marathon not a sprint. Stay humble. Like Charles said, there's a lot of work and time that goes into developing your craft. It's a never-ending process!