Note: This article is part of the How to win a Hackathon series.

Though it all starts with an idea, keep in mind it doesn’t end there. While we all want to come up with the next most innovative and original concept, remember that the past winners of Hackathons such as the Rails Rumble, have included an app that helps you keep track of your favorite beers, and another that lets you create links to all your other online sites, even though About.me and hundred other such services already existed.

When it comes to the idea for a hackathon, the most important element is that it be a concept that is easily and quickly understood. While judges will spend the time looking over the site trying to understand it, the average voter won’t. They will click on each site in the competition, look over the home page and then proceed to the next. Most won’t even sign up unless it specifically appeals to them.

I’ve seen apps finish in the top ten that didn’t even work. That’s not good, but, it shows the importance of the simplicity of the idea. As a rule of thumb, the first time visitor should be able to readily identify your concept in under 10 seconds. I believe first impression is one of the main reasons why apps finish strong in a Rumble.

While the app doesn’t have to be the next big solution, it does have to promise value to those who will be judging and voting in the hackathon. It’s very important when selecting an idea for a hackathon to understand the target audience. Again, I believe this is why the apps that have finished in the top three each year, have done so well.

There are exceptions of course, and my entry in the 2010 Rails Rumble is a great example. Going in, I had two ideas to choose between. One was a service specifically targeted at developers (the majority of those judging and voting) and the other was CommendableKids.com. I went with my heart and decided to accept that we’d not appeal to a good percentage. Thankfully, we still finished strong, and even those without kids could appreciate the goal of the site.

In the end, you and your team will have to carefully weigh the passion for an idea with it’s appeal to the target audience in making your decision, and then be sure that you clearly state the goal of the application on the home page and then fulfill the expectations you set.