I want to link a forum and a website together under the same domain name. I'm going to start with the forum and once that builds up I want to add a website under the same domain name - which is the best way to do this?
I will recommend using a cms script you can test various scripts here - www.opensourcecms.com or compare their features - www.cmsmatrix.org
Put your forum into a subdirectory, e.g. mydomain.com/forum and redirect all requests from mydomain.com to mydomain.com/forum. Once your site is ready, upload it to mydomain.com and remove redirecting.
You could also create a sub domain as in forum.mywebsite.com this would be treated as a new domain, so you dont have to worry about your original domain.