I had a friend invite me to photograph Bobby Rahal's racing team at practice in Phoenix back in 1990 or so. Thing was, I didn't own a camera, and knew literally nothing.
I read a book on sports photography (dont know who it was), then I bought a Rebel kit with a junky little lens, found a 600MM f/8 mirror for $100, and got in the car.
We arrived Friday night, drove to Phoenix International raceway in the early morning, and I proceeded to burn through 200 rolls of Kodak Gold 200.
So. I developed them as cheap as I could, and made a very important series of discoveries:
1 - If you don't know how to use a camera, shooting in the GREEN ZONE doesn't help much when the subject is moving at 180 miles per hour.
2 - Neither does setting the little dial thingie to the sports setting - in fact, that makes it worse (no blur, and the car, moving so fast, looks like it's parked on the track).
3 - Publishers have requirements. One requirement was SEND SLIDES. Oops.
4 - This publisher had an old school graphics department who accepted 8X10s in black and white. I made about 15 (at something ungodly like $18 each) and sent them in.
5 - Racing publications are both a.) cheap and b.) intolerant of n00bs.
So I paid about five hundred dollars to shoot the event. I was paid $25 for the one borderline print they took, and I cannot believe they bought that one, it was so terrible. Got to eat lunch with one of my favorite drivers, though.
The last time I shot a racing event it was a qualifying day for NASCAR at Fontana. I took twenty rolls of Sensia (bought in bulk for what, $3.50 a roll). I shot it all, and sent the whole mess to my editor who selected 20 shots, 3 of which sold for $125 each. The rest of the slides came back to me, and I made another sale to a Finnish magazine for $85.
The rest were parsed, and I recall being pleased that I only threw out 20 or so before I got picky about details. In all, 20 rolls of 24/25 (the 1N was efficient) netted a little under 500, I sold 4, and I tossed 20/25 out. Profit was low, but that's why I am a technology project manager instead of the next Annie Leibowitz.
There must be people who shoot so solidly and plan so well they never toss a shot - except any practice/setup shots they take (used to be off a Polaroid back, not...they're intentionally expendable). Me, I bracket and test and shoot from the hip sometimes - I am used to taking risks and trashing my stock because I never shot anything that stood still, and you just...never...know.
And no one - NO ONE is as critical of your work as you. These folks on this board are fair, honest, and open minded. Share your stuff, brace for negative feedback, and keep shooting.