Permission releases are another form of contracts, although a more informal kind. In them, you are giving permission for the magazine or company to use your work for an agreed-upon sum or reward.
Watch for weird clauses. Know what rights you're giving up, and weigh them against what you're being paid or the prestige of the magazine. There are shady zines that will steal your words for no payment, so watch out.
Photo releases. Sometimes big magazines will want your photo in the bio line, and will ask for a photo release. Make sure these are photos that you or your family took and are not copyrighted photos with a professional photographer. Senior portraits won't qualify most of the time. Choose a good pic of yourself!
Always know your goals. The best situation is when you allow a magazine to publish your story with First North American Rights or minimal rights given, for a large sum of money or prestigious publication. However, you usually have to decide what's most important: getting published, being published again, payment and prestige. Don't be in such a hurry to get published that you make the mistake of selling your work for little profit.
If your story is publishable, you are worth being paid well. Read carefully and keep copies of all your contracts. It's good practice for later life, or so my parents tell me.