Identify your niche. There are many special groups of people who are underrepresented in online dating sites. Your site can be targeted to specific geographic niches or base it on physical characteristics or religion. Targeted sites often bring more passionate users, and can carry more targeted advertising, which yields higher revenue per view.
Think of a catchy name for your dating website. It should be easy to remember, and ideally contain a keyword relevant to your dating niche. For example, if your dating site caters to Jewish users, you might try something like "jewishconnect.com" or something along those lines.
Design an interesting, engaging website with HTML or a visual editor like Adobe's Dreamweaver. Some features to consider might be user ratings to show the most attractive people on the front page, a system to allow mailings and comments between users, and advanced search functionality to search by specialized attributes. For all of this, you will need a solid understanding of database technology, such as MySQL.
Register for an advertising account with AdBrite or Google's AdSense. Each will give you a chunk of HTML code that you will then need to place on each page where you want advertising to appear. As you gain traffic and receive more clicks, your income from these advertisers will grow and grow.
Consider tying a blog into your site. Since it's a dating site, good posts might contain advice for finding love online, how to meet new people, date ideas or simply instructions on how to use the dating site's services. This is a great place to expand coverage of little-known features that the majority of your users might not even know about.