Another Newbie question:

I have about 20 domains that I purchased with the intent of redirecting traffic to my principal domain. My question is do I need to host each of the domains to take advantage of SEO techniques or will the techniques work just as well with domains that are simply parked?

I would assume theyd need to be hosted. Go to BounceWeb. Unlimited domains hosted for 4.99 a month.

You have to "addon" them to your webhost's cpanel.