"Journaling is one of the most powerful tools we have to transform our lives." - Deepak Chopra
This one is easy to begin with, just write down whatever comes to mind. If your mind has been feeling loud writing it all out can help you return to a sense of calm.
Each night write down just the best parts of the day.
Writing down whatever you remember from your dreams can increase the amount of dreams you remember each night. It may even help with sleep quality.
Keeping a food diary can help you find which foods make you feel good and which ones are causing you problems.