I've had my own sports photography business for 25 years. First I was a sole prop., then LLC and now Corp.
My first advice is make sure you really love what you are doing because you will be living and breathing it for quite awhile if you want it to be a success.
Second, find an accountant that is good but more importantly one that you click with. I am so lucky to have a cpa that is so good and yet we can laugh together. I am also out to her which makes it easier when I have questions that involve my partner and the business. A good accountant will keep you legal. I'm horrible at entering checks, keeping track of receipts, etc. I use quickbooks and she is always helping stay up to date. As I always tell her "I don't look good in stripes."
Identify what makes you different from everyone else that does the same thing you are doing. On what level do you want to compete? Prices, services, etc. Some people want to be like wal-mart and be the lowest in price. Personally, we freely admit we are not the lowest priced but we do offer the best service and best products. If they are simply looking at prices, we won't work well together.
Timing is also important to any business. You can have the the business but sometimes, everything doesn't click at the right time. When it does, it's great.
Oh, one more thing. Always keep in mind that you are never the boss. Your customer is the boss, Period. People always say to me "oh it must be so great to be your own boss." Yeah, right...I have several thousand bosses and each one always lets me know it too.