Visiting an onsen (hot spring bath) in Japan is a wonderful experience, but somewhat intimidating if you haven't been before and don't have a friend to show you the ropes. Due to the volcanic and geothermal activity all over Japan, there are natural hot springs in many areas. The attraction of many hot springs seems to be the location (many are in beautiful areas,. like Shirogane onsen that I visited in Hokkaido) but also the water itself which is claimed to have various therapeutic effects due to mineral content. Some onsen are just public baths where you pay a fee, do your thing and then leave, while others are part of hotels. Bathing seems to have been an integral part of Japanese culture for centuries, and is used for relaxation and socializing. An important point: THE BATH IS NOT FOR WASHING (see below)!
Ok, here's the basic procedure:
1. If you are staying in an onsen hotel, you usually will be wearing a yukatas (light kimono-type robe) and slippers around the public areas. Inside the entrance of the bath area, there will be sort of a locker room with a bunch of baskets where you leave ALL your clothes.
2. Inside the bath area there will be a row of hand-held showers with soap, buckets and a very short stool. This is where you wash to when you enter the bath itself you are totally clean, with every trace of soap removed.
2. Most onsen seem to have several baths you can choose, often outdoor and indoor. At Shirogane onsen, there was one bath that was a 5 min walk down a path towards the river. There was a wooden shack at the bath with separate areas for men and women to disrobe, but the bath itself was mixed (yes, naked men and women in the same bath) The other bath there were segregated with both indoor and outdoor baths. The water temperature ranges from hot to really hot to *&^%$ hot so you have to ease yourself in, but once you get used to it, incredibly relaxing. You take a very small washcloth size towel with you to the bath which you can use for modesty purposes if you must, or to wipe your face. People like to wear it on their head while in the bath, so it doesn't get misplaced I guess.
Given the high water temperature, you can't stay immersed for a very long time, and drinking alcohol before probably is a bad idea since your blood pressure may get too low. Once you have had enough, you try to dru yourself with the micro towel sand then go back to the dressing area where there are larger towels, and you can put your yukata or clothes back on. Rehydration (with water, not beer or sake, at least not at first)is important since you can get dehydrated. After that, you will be very relaxed and probably sleep very well that night.