The art of onsen
The jigoku-onsen I showed in my post about Beppu are an exception. Onsens are usually for bathing and you don't want to miss that experience if you go to Japan! Being a foreigner, some people may discretely stare at you, but thankfully it rarely happens. In fact, they are just worried that you might not respect the bathing etiquette, which is very easy to follow...provided you know it! Here is a quick explanation.
The most important thing you need to know is that you must wash yourself BEFORE entering the bath. There is usually a shower area:
Sit down and wash yourself thoroughly. Soap and shampoo are usually supplied and it is common practice to bring a small towel to use as a wash cloth (you can find one at any 100-yen shop, and most onsens also sell them). If you're being stared at, it suddenly stops when you start washing yourself.
Depending on the onsen, there may be one final thing you need to do before entering the bath. If you see a small tub like this:
With something like かけ湯 or かき湯, which literally means "hot water to pour", usually written, then you have to pour some of that water on your body a couple times. I don't know why this is part of the procedure as you're already clean by now, it must be some kind of ritual.
That's it! You can now relax. Depending on the onsen, the number and size of baths can vary as well as the water composition, environment etc...For me, the best is to bathe outdoor in winter in a beautiful, natural environment, it's just fantastic!
Here are some types of baths. Standard:
But also jacuzzi, cascade bath, electric bath, steam bath...
If you're a couple, you should also keep in mind that some private baths can be reserved for an hour or so...I strongly recommend that!
By the way, outdoor baths are called rotenburo (露天風呂)...
A final detail, that might represent a problem to some: in an onsen, one bathes naked. Men and women are usually in different sections, but mixed-bathing onsen can still be found in some remote areas...pretty rare though.
Oh, and take your time. The purpose of an onsen is to relax...