If someone comes to you to report a problem that they need fixed or to make a new request, and you ask them what the priority is, what's the most likely answer they'll give you? High, or very high! Very few times will it be a low priority, because if it is, often they won't even bother bringing it to you. So everything that comes to you can potentially be considered high priority by someone. There needs to be a better way.
Determine the business impact of their problem or change request. Find out what happens in the real world, that someone cares about, if their problem doesn't get addressed or if you're unable to complete their new request. A few years back, I began using the term "tangible impact." Will money be lost, saved, or earned, and if so, how much over what period of time? Will labor hours be saved or lost one way or another? How much time lost or saved?
When you get the answers to these questions, you should have the tangible impact, and you'll have a much better way to prioritize issues since you can't do them all at the same time. If you follow this practice, prioritizing issues will become a more straightforward exercise, as will getting everyone on the same page.
I'd love to hear your thoughts on this!