One of the things you can notice when you will travel to Japan or when you will stay here is that there are many onsens where you can go and enjoy a relaxing atmosphere and let your feeling be at peace. But in Japan, there are differences. That is why you may be able to commit some things you should not do. That is why it is the best that you will know what are those etiquettes you should be aware of and practice it.
One etiquette is that anyone who will enter into the bath should take a shower first and clean himself or herself. There are already installed materials that one will need in the bathing areas. Make sure to wash and rinse well as it is not good you are with soap or some dirt on.
As there is mixed bath then you should be aware as they may require you to wear a swimsuit. The towels would be normally be brought by the guests themselves and they are usually put on the side of the bathing area as they are not allowed to be soaked in the water.
That is why you should bring your own and you can fold it and put it in your head so you can use it as you finish.
Be sure also not to be noisy when you are in the bath. Most people go there to be relaxed so do not destroy it. The children who make splashes are usually tolerated.