Rule #1: Keep it simple.

My quick credentials: 33y/o geekboy, been casually coding for 25 of 'em. Ex-professional developer, trying hard to never write code for others again. I am not a project manager but I'm going to half-pretend I am here for a bit.

I'm not active in the coding parts of it, but I've been a redditor for about 2.5years. I've seen a lot of awesome ideas for projects pop up since I've been a member. Awesome ideas that a lot of people flock to, get excited about, and then never finish.

Do you have an idea for the next great MMO? Hey, me too! Do you have an army of animators to help make it? Yeah, me either. I couldn't even find an artist to help me with my turn-based strategy game.

If you're reading this, then you're probably familiar with the amount of work it takes to code the most trivial of tasks. If you've worked in a professional environment, then you're also familiar with how difficult it can be to maintain a project and codebase with many people working on it.

So's here's my suggestion: keep it simple. Want to make a game? Take a look at indie games like QWOP, games with a simple mechanic that's fun to play with. Try to think along those lines.

Another important factor, and I think this is where a lot of reddit projects fail, is intelligent distribution of labor. You're a lot less likely to get a finished project if someone is just "the art guy", someone else "the coder guy", etc..

Every project needs a strong, central figure to guide it. Whoever that may be is going to need some serious project management skills. Don't kill yourself writing documentation, but do document as you plan and constantly as you work.

You're going to need to be ready and dissect the project into the smallest parts possible. Why? Because people can only do one thing at a time. And you can't even really count of them to do that since you're not paying them. Giving out smaller 'assignments' to volunteers helps increase the odds that they'll contribute and decreases the damage when they don't.

Plus there's a certain psychology to it. We coders and creative types, we like to be done with things. We've learned to enjoy making it, but really we like to be done and marvel in all its glory and how clever we are. Smaller assignments keep people engaged and feeling like they're contributing more than if they are bogged down with a larger part.

Finally, it might be a good starting point to decide what platform you're aiming for. It's probably not a popular idea (and I am full of those lately,) but I'm personally interested in the possibilities of HTML5/ jQuery since both become inherently more powerful as browsers improve. (My roommate has given me a fetish for node.js for server code but I have not used it myself.)