I just keep track of mine by remembering, but keeping a diary may have allowed me to find some earlier, especially where they had milder effects.
If I was going to do a diary I would record the moods, stresses, any use of alcohol or other drugs (best avoided) and other health symptoms. Most of my depression is caused by stress or illness. Anything viral and post-viral, or sinusitis, or severe allergy causes me to become depressed. Basically anything that affects my immune system. I spent most of last summers bushfires feeling depressed due to the smoke. Alcohol is a problem, so I don't drink it. After the depression I go fairly high and then return to my more "normal" mild hypomania. Stress tends to make the variation more pronounced.
