How Do You Test A New Site Idea Out Successfully?

So you have a new idea for a site, you have some content and you have a design but, how do you go about testing whether there is a demand for the type of content or whether the site is going to work when launched?

Im sure we all have our own unique methods when it comes to testing out whether a site concept is going to work or not so i thought i would ask how you do it.

For us, the best method we have found in the past to test out new site concepts is to make 2 versions of each site, one for the search engines and one for an AEN / AVS system. By sending our own traffic to both types of site we can generally get a good idea whether or not the demand for the content is there and, more importantly, how well the content will sell at any given price point.

So what do you do when trying out new site ideas? Do you even test them out first? If so, how? Also, what in your opinion is a good amount of traffic to send to a new site concept to make sure the testing stages are fair?

Regards,

Lee

... I ask you.