In general, make sure you get regular updates on progress. Besides that, I would recommend you adopt the Agile methodology for the software project or have the software delivered in iterations so that you can touch and feel parts of the application. It minimizes risk and everyone can ensure the requirements are getting met early. Define the first iteration and then it'll be a deliverable in like a couple of weeks or so. Then you can gauge how things are going. Attitude of developer is also important. You don't want someone who thinks they know more than you or is better than you. Changes will be harder to make with that attitude. There's lots of other things, but those are a few pointers