I've spent many hours on these kinds of sites, talking to members, using the features, and generally trying to see if the sites offer what they say they do, while still trying to keep my (and your) privacy intact.
It's a tricky juggling act, and for most folks I'd recommend hitting the club or bar before trying anything else.
It offers a high degree of privacy if you're also seeking a romantic relationship, and you can target your profile precisely to what you're after.
Everyone who joins has to pay to gain access - a great filter for 'professionals' or lookie-loos - and their set-up is pretty swanky. The majority of the site's users are North American; folks living in Asian or Europe might struggle to find anyone.: Show something provocative in your profile, minus any nudity. Take a peek at your competition, and make sure that you're avoiding all the dating cliches.
For open-minded, adventurous singles and couples, Fet Life might be something to check out.
Make it clear who you will, and refuse, to respond to - most folks on Fet take "no" graciously - although some may get off on it.
Posting in groups specific to your desires will amp up your chances of finding someone fantastic, however be prepared to wade through a tremendous number of replies, first.
If there's one type of'dating site that has blanketed the internet, it's those that cater to folks seeking something more casual.
Unfortunately with said plethora of sites comes the difficult task of finding the right site with a decent price and actual members that exist outside of a professional relationship - if you get my drift.
Profiles allow you to get to know them a little bit first and to help you decide if you want to start the conversation.