The phrase from Field of Dreams 'if you build it, they will come' has no meaning when building a web site. If you don't build traffic to your site, no one will ever find it. 100Kaffiliates.com provides you an introductory guide to the most practiced ways of building traffic to your web sites.
Check out 100Kaffiliates basic SEO guide for more information.
Write articles and comment on people's blogs. Always include your web site url in the signature of your article/forum post. Internet forums are also a great way of generating traffic to your web site.
There is many advertising networks out there that you can advertise your site on. Google and Yahoo both run great advertising networks that are well trusted and been around for a long time.
A practice that has popped up lately is buying deleted domains that already has a steady flow of traffic to them. This practice is most used in Adult Marketing.
There is many traffic brokers out there promising tons of quality traffic. Research all traffic brokers before you sign up with one. There is many scams associated with this type of traffic, BEWARE!
Always be on the look out for ways to generate traffic to your site. Starting with an affiliate program that you have interest in or are familiar with will help you "think out of the box".