The first and most important step is to understand the goals of your hackathon. Are you looking kick-start an open data developer community around your data? Do you want to inspire or incubate local startups to join in the effort? Are you trying to connect developers with local community leaders? Depending on your goals, you may want to tweak the recipe given below to give you the best results.
It’s also important to understand your constraints. Google, Amazon, and Microsoft weren’t built in a day, so don’t expect the next killer iPhone or Android app to be completely built within an 8-hour hackathon. But, by providing a group of developers a forum to meet, inspiring them with hard problems, and supplying them with data to drive their applications, you might just spark the next innovative company or solve real problems in your community.