[asher_]

Find agreement on priorities with short meetings on a regular basis. This can be done in a structured as part of Agile, or just as regular meetings to get everyone on the same page.

The approach I take is that I don't care what the order of the list should be (save for dependencies), so I give collective control over that to other stakeholders.

If someone then comes to me a few days later with an "urgent" request that will take a non-trivial amount of time, I simply put the pressure back on them to seek agreement on the change of priorities. They can make their case to the other stakeholders about why their project or task is more urgent or important than others on the list, and come back to me if/when they have that.

The extra benefit to this is that when other tasks are not finished when they were originally expected to be and you are called on this by a stakeholder, you can point out that they agreed to add new higher priority tasks into the queue, so the original time estimates were no longer applicable.