OnaClubs are rad and I love them.
I'll try to give a quick/decent rundown on how they work.
All the shops I've ever used are outcall but they almost always have a contract with a couple rental rooms in the area and will make the reservation for you.
In most cases you get to the general vicinity of the rental rooms (usually the site will have instructions on where to go to after you leave the station), call them up to confirm your arrival and they'll give you the name of the rental room and directions.
A couple shops (notably Lovely Hand in Shinjuku) are more like hotel health where you stop by an actual booth, pay them there and they give you directions to the room.
"Traditional" OnaClub are literally just services where you pay a girl to watch YOU masturbate. No touching, no nothing. Almost all shops now, though, include a HJ as part of the base package. Some still do offer "no touch" courses, though, but those are more of a specialty thing.
That said if you just go for the basic course its almost always the girl fully dressed and no touching on your part. That's where the ala-carte options come in - for an additional fee you add on all kinds of stuff. Usually OnaClubs stop short of sumata/AF - "health" services. BJs are also usually prohibitively expensive. If you're in the market for a BJ or sumata a DH is almost always a better option.
The upside of this, though, is that in MOST cases (notice I said most) the girls are significantly more attractive than the girls working at a mid to low level DH. If you are smart about your options and don't mind forgoing some of the more "hard" services you can spend time with a very cute girl for 10,000 JPY or less.
One other bonus of OnaClubs is that you are pretty much getting uninterrupted service to your member for the whole course. There's usually no shower at the beginning (just a simple wipe down) and a few minutes to get cleaned up at the end so if you book a 45 minute course chances are good you're getting 35 minutes of stimulation. Its a lot of bang for your buck.
One additional plus is that for OnaClubs its very rare for girls to be off-limits to foreigners. Unlike DH where its almost always on a case-by-case basis for OnaClubs its very rare for a girl to be unavailable.
A few tips for OnaClubs from my own experience -
* Start with a 30 minute course or so. I like long courses (60 minutes) myself but a lot of these places have ultra-short (15 or 20 minute courses) which are pretty cheap but extending the course can be expensive/not possible if the girl has another booking.
* Pay the upcharge for higher ranked girls. Unlike DH where you can be looking at an additional 5000 JPY plus for high ranked girls for OnaClubs its usually a 500 or 1000 JPY upcharge and its almost always worth it. Trust me on this.
* Don't go nuts on the options right off the bat. Start off with a few, see what you like and then ramp up a bit. if you book a 30 minute course and add on a ton of options there's a good chance you won't be able to really make use of all of them and will waste some cash. Check a few shops and see what is more/less expensive at that particular shop. For example all nude is a pretty good deal at Lovely Hand but at Unpretei you're going to save a decent amount of cash just going with all lingerie.
* Have a second option in mind in case your first girl ends up calling sick/isn't available. Lots of these places have huge rosters and some of the girls call in sick a lot. I don't think its really "sakura" (dummy profiles, etc) like you see at some DH, more that its just a pretty loose employment system.
* Since this is much less of a "all-in" package like you'd get at a soap/LH you'll need some Japanese skills to navigate everything. Lovely Hand has an English site and is definitely a much easier option if you're not confident in your language skills. Some of the other shops might pose a slightly higher hurdle.
