Fortuitously, I've just been working on this.
In Keith Ferrazzi's amazing book Never Eat Alone, he writes about his Three-Year Plans. Now, I don't like Plans. I associate them with communist Five-Year Plans and long meetings and rigidity.
But these plans were wonderfully lightweight, as he described them. So I tried them.
I scribbled down several areas of my life that I want to change over the next few years -- writing, programming, drawing, etc. I then took a fresh piece of paper, titled it "Writer," and scribbled down what I'd like my life to be like, from a writing perspective, in three years. I directed those scribbles into specifics. How many stories do I want written by then? 10? 50? And what kind?
That became a great feed for my Projects. That Plan is now part of my weekly review, and is something I just think about a lot.
These Plans help me prioritize my Projects. The Projects that support these Plans are more important to me than, say, repairing the dryer vent.