If your hair feels dry and damaged, that's another indicator. For a week before mine fell out, it felt like it didn't belong to me. Hard to describe but not pleasant. I used to run my hands through my hair first thing in the morning. The first indication was a lot of hairs on my hands, but not clumps. I had already organised to get my hair cut really short and did it that day. Short hairs falling out are easier to deal with (practically and emotionally) than long ones. Shaving of course is the other option. Once it started, my hair went pretty rapidly. I had some sleep caps (helped with the sore head) and simply emptied it out over the bathroom sink in the morning!