I strongly suggest trying out tons of bikes at the bike shop. Go to a few shops, and try both new and used models. Try road bikes, hybrids, and everything else they have.
I have come to realize that one bike might not be the answer every bike-need a person has though. I love my trek hybrid and wouldn’t use anything else to commute to work, but for long, faster rides on the weekend, my hybrid is too heavy and slow. I got the hybrid because I did not feel safe riding in DC traffic on a road bike (I like being upright in traffic), and also because I know that at 7am when I am sleep deprived and biking to work, I need something a little more stable and able to handle gravel and uneven pavement. Either end of this season or early next (whenever I can find a good sale and have money), I plan to buy a decent road bike for weekend use. But as a commuter bike and for rides under 30 miles, the hybrid is awesome.
Also, ask your friends what type of bikes they have if you plan to ride with them. One influence on my purchase choice was that all of my friends have hybrids or similar models. It means we all go the same speed and are wary of the same type of obstacles in the path, which makes group riding easier and more fun.
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