Choose your topic or question. If you are known as the go-to person among your friends or family for help with a particular area, that might be a good one to choose. Once you've compiled some good open resources, it will be easy to share them any time people come to you with questions. You could also select a topic you are interested in learning more about, or one on which you consider yourself an expert, even if no one else does. 

Discuss whether or not there might be open content that answers your question. You might also consider where you have looked for resources on this subject before, and what kind of resources you have found. 

This screencast on how to spot openly licensed content will help you. (Make screencast)