In addition to much of the great advice here, I find reviewing the NHC winning recipes posted by the AHA (one of the many great perks of being a card carrying member) helps when developing a recipe. I look at multiple winning examples of the same style and look for similarities. In particular, I look at things like grain %'s, hop schedules, yeast used, fermentation profiles, and mash profiles. The similarities as well as the differences you find can help you get a good starting point.
It's a bit daunting at first, but once I started learning more about various ingredients, it has helped me out. I've also received great advice on specific recipes I'm planning from this forum.
For my first brew I found a great clone recipe and brewed that. That way I stood a better chance of coming up with something that I knew I would like. I've known on or two guys who went wild with their first brew and made a very complicated beer that ended up undrinkable. Turned them off of brewing. A cherry bourbon vanilla imperial porter, may sound good, but it's not easy to nail something like that and can get nasty if you overdo things.
My advice is start simple with basic and proven recipes until you get your process down. Also seek out a few good commercial examples of any style you're interested in. You might find that it sounds better than it tastes to you. 5 gallons is a lot to go through if you don't really like the beer.