Do your homework. Shop around and ask for price on the phone. If they are not prepared to give it, tell them to forget it!
Ask how many meetings, with how many different people, you get for the quoted price.
Don't be duped by bait advertising. Remember, ads that mention "Good looking men with fab abs", for example, are not usually as good as they first appear.
Never give credit card details over the phone
Insist on a contract with a set fee written on it, and make sure you get that service without having to upgrade your memberships. This is when a customer who doesn't like their first date asks for another and is often asked to pay more money for a "higher calibre" client.
Never sign straight away. Take the contract home overnight to consider.
Check out the bona fides of a firm.
Be wary of agencies that promise unlimited or a large number of introductions. Get them to pin point a number - for example, "We guarantee at least four introductions." Legally, you can hold them to this.
Find out the criteria used for finding your partner. Do they use a written questionnaire or conduct an in-depth interview?
Find out how stringent security measures are at the agency. Did they ask your prospective date for ID? Also, make sure your name and address isn't distributed randomly to other clients.