Im thinking of taking a shot at affiliate marketing. I want to put some sites under a generic domain to test. Can I get away with "www.mydomain.com/worldsbestpoker" or "www.mydomain.com/hotelrewards" Like that? Or is this a no-no?
Those aren't subdomains, they're folders. This would be a subdomain: worldsbestpoker.mydomain.com Obviously, with http:// in front of it. Many ad networks do not accept subdomains.
What you have just asked is how about 99% of people do it. That is not a sub domain, but a directory of a site. Sub domains are: games.domainname.com.