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 because once you've compiled some good open resources, it will be easy to share them next time someone comes 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. Have you looked for resources on this subject before? If so, what kind of resources you have found?