Do The Project Yourself First!
The only real trick to Project Based Learning is doing the project yourself first. Remeber that PBL is a constructivist idea and the center of that is doing and making. I have heard a lot of reasons over the years not to do the project first, and they all seem like excuses. I honestly do not think it could ever hurt to have done what you ask others to do before you ask them to do it. We learn if it is relevant to the subject you teach if it will enhance understanding and entice your students to be engaged. We also find out if it is fun or a drag.
Do anything, fall out of a chair, research gravity, statics and draw or take a picture of your self-falling, and explain what is going on, Newton did less.
Use your knowledge of your subject area to do, define or create something. Video or photograph it, do a small write up and email it to me. We can start there.
These are some of my examples of doing the project myself first.
Classic Self-Help Book