I've been to a few onsens, but never a sento (public bath). I did go to Oedo Onsen Monogatari many years ago, but that's more of a theme park. But since I live in Japan now, I decided to do as the locals do and visit a nearby sento.
The sento I picked stays open until 2am, so it's a good option for relaxation after work. It was 460Y for entry, with an additional 100Y for bath and face towels. There was a common area with a TV, vending machines and bath items for sale. The attendant was an old lady who spoke only Japanese, but fortunately not much communication was required.
Inside the changing area, lockers were provided with a refundable 100Y deposit. There were also vending machines with cold drinks. I was confused about where to place my towel, and decided to leave it in one corner of the changing area, until an old lady pointed out that I should leave it in the locker, or else the staff would take it away, thinking it was a lost/dirty item. The old ladies in there were friendly and probably figured it was my first time there. (Everyone else was probably wondering why there was a 外人 at their local bath, and indeed I was the only one there.) As for the nudity, it was surprisingly easy to get used to, as everyone's nonchalant about it.
The next step was to take a shower. I noticed people had brought in their own bath items. There's a good reason for this; the bath provides basic shampoo and soap, but for someone like me who has poor hair quality (frizzy hair) and who needs hair products geared towards that, I should have brought my own. I personally think it's too troublesome to bring full-sized shampoo and conditioner from your place, unless you have travel ones. I suppose there's also the option of buying it at the sento.
On to the actual bath. There were a few different sections - a hot jacuzzi bath, and a cold still bath. I have low blood pressure, so I get dizzy easily in hot baths. Hence I try to get out of the bath every 5-10 minutes or so. I soaked my legs in the cold bath so that I would feel refreshed rather than sleepy at the end. After drying off, I made use of their hair dryers, which were provided at 20Y for 3 minutes.
Overall, it was an enjoyable experience (who doesn't enjoy hot baths?), but I probably won't go back to often. Mainly because of the hair product inconvenience, and that it's a rather expensive way to get clean.