So I had to do a ton of author bios recently before sending off my manuscript... It's hard stuff let me tell you. Here are some tips that I've found through research that helped shape my bio and make it better.
Third Person. It's annoying as hell but every single page says to write a bio in third person. It feels pretty weird writing about yourself in the third person but I guess it's what you're supposed to do. Even if you didn't want you, I-I-I gets pretty old fast. Do what the sites say and write in third.
Don't mention personal life. Whoever is going to read your author bio, whether that be literary agent, editor or publisher they don't care about your dog, cat, shoe size or hair color. Only mention something if it deals with your project or has to do with writing or literature.
Mention organizations you belong to. You don't have to mention those that don't have to do with reading. For example I am part of an exclusive writing group on yahoo. They only let in certain people and you have to have references. I brought this into my bio and mentioned the creator, who is a notable author. This makes me seem established and involved with author communities.
Mention any writing awards or mentions you have. I mean this is pretty obvious. If you haven't won anything then don't say anything. It's always good to boast a little. You want the person reading to know you are worth it after all.
Tell them about your social presence. If you run a book related blog tell them. This is a huge one! If they know you have hundreds of twitter followers, facebook friends and blog followers this is a huge plus. They love to see that other people believe in you.
HMMM. I can't think of anything else. Does anyone have anything else to add? These are hard, right? It's not just me.