These guidelines are just ideas to think about before releasing the shutter of a camera at a sporting event. Sometimes guidelines are meant to be broken, especially if you are a non professional, or an artist.
The guidelines are mainly for those that want to go professional and sell photos to magazines and news papers.
The youth level, however, for the parent, the coach, or the youth player, the guidelines should always be seen as a way to compliment the image, and not something set in stone.
15) Bring extra everything with you especially batteries, you will need it.
17) Make sure your horizon is level. If it's art your after, then this guideline is up for grabs. If it's a good photograph your after, then this is an important guideline.
18) When editing your images, never edit out, or crop out the chin of a player. The eye's and above are OK to edit out but never the chin and below. Make sure skin tones are realistic and consistent. Remember to keep a story in mind weather it is an action shot or a simple head shot. Head shot too can tell a simple story, weather its dirt on the face, a tilt of the helmet, a blink of an eye...
19) Shooting in the RAW format gives you more flexibility when shooting and especially when editing. Shooting JPEG is faster, but RAW is better. Learn RAW.
20) Carry a second camera with you with a lens set that complements the first camera. Bring appropriate camera gear you will need to get the appropriate shot. Once your at the venue, it is a big pain to go back home to get something you forgot. Being prepared is key.
21) Bring business cards, especially if you are shooting other peoples youth players. Parents are curious to know who is taking photo's of their kids because there are a bunch of sicko's out there exploiting the kids on the internet. At the very least, carry business cards so you can trump up business, get your name out there in the market and get clients.