Here are some tips on promoting your online dating site

Aim locally
Dating sites work when people can contact other people. Aiming globally spreads it too thin. If you can corner the market in your area then you can expand to other pockets in your state/region.

Don't allow visitors to access your site without signing up
After a visitor signs up, force profile creation before giving them access. This will help build your member database. If people come to your site and see that it's empty, no-one is going to join and create a profile.

Get listed in every dating directory
Since they dominate the search engines and get tons of visitors.

If you have deep pockets
Look at starting an affiliate program and pay for each lead/free sign-up.

Set a PPC budget
Target some long tail keywords.

Set-up a SEO plan
Work on it a little every day. You could see top rankings in a year if you do things right.

Print some business cards
Hand out business cards where ever you go

Target singles and swingers
Target singles and swingers in different social networking sites.

Forget about guys
Guys will always come. You need chicks. Find a way to get them and make them active. They are the stock on the shelves.

Be patient
It's going to take time - especially if you're not throwing a lot of money into marketing your site.