I am a Software Engineer and over the past few years I have become the de-facto software project manager simply because there isn't one. So to keep our sanity in the R&D/Engineering department, customers have become accustomed to coming to me with their requests. I have no experience in this realm so it is my first time acting as a project manager for software projects. I have managed other things but not software.

So, how do you manage software projects and mark priorities? Requests come in at infrequent intervals so we very well could be working on something for someone else and then another person comes in with a "rush" job that needs working on. Is it easier to just say First Come, First Serve or is it the person with the most money?