I keep coming back to a simple tool created by Dan Sullivan. It is easy to use and provides consistent, powerful results. It's a one page resource that you can download directly from the Strategic Coach website.
The tool focuses on five key questions (paraphrased below):
What do you want to accomplish and why (purpose/motivation)?
Why is this accomplishment important (what impact would it have for you and others)?
What is the ideal outcome (what would the finished result look like)?
Do you really care? What is the best result if you succeed? What is the worst result if you don't?
How will you define success (what are the criteria)?
Feel free to check out this resource for yourself, it's a free download, and you might find it helpful for some of the projects that you are working on!