Well, it is a big question and could take up a lot of time covering everything. However, for the purpose of your sanity, I think there are four main ways to generate revenue:
Set up afiliate relationships on your site
Offer adsense or similar ad network ads
Sell ads directly on pages where you are not selling anything
Sell sponsorships on key pages with excellent traffic levels
Of course, you can do all of these things and test to see which is the best
one for you.
A lot of this does depend on your content and if it is a B2B or B2C website. We are sometimes turned on and off by different things at different times and some ads work better on some websites than others.
Of course, blogs and forums are also opportunties to sell ads now and specific categories could net you a sponsorship deal showing the advertisers banner, logo or even playing an audio or video.
There are loads of options but it does depend on a few fundamental points relating to your design and your audience. More to come I am sure!
Sellads
