There are a few ways to do this. I start by thinking about the things that are most important. Is this going to affect anything else I need to do? Did I promise I would do this to myself or anyone else? Is it life threatening or important for anyone's health or safety? If the answer to all of my to dos are no or yes I choose by what I WANT to do. Then, if I really can't narrow it down to three I'd put them all in a hat and pick three out each day.