Written by an ex-agency worker turned indie.
Not sure if I've got anything truly definitive enough advice-wise to be worth putting on the main site, but I wanted a place to write my ideas about finding relatively reputable parlours/agencies since I get asked about this a lot!
What I usually say when asked about London agencies is that although I used to work for two, I am not comfortable recommending them to anyone now that I know what being indie is like – I can't possibly advise someone to potentially give a third of their earnings to people who may not actually be doing all your security for you, or finding you good clients, or anything you can't do much better yourself!
However, of course agencies and parlours can have their advantages and lots of newbies (like I did) feel more comfortable of the idea of not starting out totally alone. When you've got no idea where to start but need to start finding out something about existing agencies and parlours, I usually recommend looking at the review sites that punters use (pop Punternet or Punterlink into Google if you don't know them already!), because these are places where punters report on reliability, quality and services etc at establishments and with agency girls as well as indie ones. They're big sites but rummaging through them is worth it. Of course, don't forget that the reviews and discussions are from the point of view of the client rather than the sex workers, so it's not perfect but it's definitely possible to get a good idea of which parlours and agencies are the most popular.
If a place is popular, that will often positively correlate to the happiness of the women working there. Make sure to read bad reviews and reports even more carefully than good ones for clues about the state of the place (flats etc), facilities, unhappy escorts etc. It's important to read everything you can find because one report alone isn't much good, and definitely don't let your hopes that a fancy-sounding agency isn't a scam affect your judgement!
Another step is to check the sex worker forums – searching SAAFE's forum using the search form and also registering on Guild of Harlots (see Google) if you can are good ideas. We can't talk about agencies much on the forum because links are not allowed (we don't want to be advertising for them!) and many of us are indies. But there's no reason not to use PMs and gather information, as long as you look at everything with a sharp eye. Also, I'd be a bit worried about information on the main site going out of date; if someone writes a post in October 2010 about how Super Klassy Agency For Winners is the best but it 'changes management' and gets taken over by a creepy bloke who pervs on the women on his books the month afterwards, some newbies might still glance over this forum and decide to join that agency, with unpleasant results!
At the end of the day, nothing beats applying to an agency or calling a parlour and giving it a proper inspection yourself. From the start, they should agree to meet for a one-on-one chat in a public place so that you can have all your questions answered and they can check out your appearance and manner. If they can't even do this part properly then kick them to the curb straight away! You should never, ever need to give your full personal information (including showing your passport etc) to an agency. If you meet them but you feel like they're evasive with any of your questions, or if they ask you anything inappropriate (there are perfectly decent ways to discuss services and stuff without anything getting uncomfortable), or if you simply find that they aren't the agency you're looking for, then again, move on with your search. You don't owe anyone anything.
Don't forget: Confirm with the agency/parlour that it's cash up-front with all clients, that there is a security procedure, and how they want you to pay your commission. Usual commission is 30-40% – more if you'll be using their flat(s) to work from, or if they provide you with drivers. I believe parlours have a similar sort of commission but it can vary a lot more. You should be able to check out their location and premises if you meet the owner there for the interview.
Finally, don't forget that even if you've been working with an agency for ages, as long as you've paid your commission you don't owe them anything else. If they stop sending you many clients, or send you too many bad clients, or ever send you to see anyone dangerous, remember that you're the one who is actually employing them to do things for you so feel free to let them go if you're not happy. Badly-run agencies and brothels rely on sex workers feeling too uncertain or trapped to leave.
From my experience with two agencies, neither were quite as hot on security or checking of clients as they'd told me they were in our interviews and they sent me to see multiple clients who were the kinds of guys I'd never accept an appointment from as an indie. Also, working with an agency can cause you to feel an extra pressure to work sometimes when perhaps you'd prefer a day off – at the worst, they can threaten to take you off their books altogether if you don't see x or y client when he demands. So keep an eye on your general levels of happiness with anyone who expects 30% or more of your earnings because if you aren't happy with them, you don't need to keep paying them – well-managed indie work with a security buddy can be safer and more lucrative, too.