Looking at the answers given, it's the definitive answer to problems like this, there's no written solution, everyone starts with the more interested domain (DB detailed design, UML use cases, requirements documentation). Well, in a theoretical world where everything goes right, if you have no problems concerning time, team and budget (I don't think this case is ever possible even in big firms), well start with RUP or start with XP. My advice (PERSONAL) is to start with analyzing requirements, dividing them into smaller one, start to think to possible solutions, and produce some paper and ink concepts about your idea. After that start to analyze one by one those smaller requirements and write detailed use case, defining as well as possible actors, those will be your domain, keep in mind, modeling well your domain is a first step to the success. Good luck with your job ! :-D Grava