Digging through the blog of the late Seth Roberts, I find many gems. Here is his concise summary of how to do self-experimentation. He mentions intending to write a book about this, but as far as I know it was never finished:
if you want to figure something out via data collection:
1. Do something. Don’t give up before starting.
2. Keep doing something. Science is more drudgery than scientists usually say.
3. Be minimal.
4. Use scientific tools (e.g., graphs), but don’t listen to scientists who say don’t do X or Y.
5. Post your results.
Worth reading the entire four-part blog post.