How to create your own forum and have a fighting chance of it not sucking:
1) Become really popular on at least one and preferably more than one other forum with a similar interest to the one you want to start. This could take awhile.
2) Have that forum reach a point where people are so flustered with the site mods/new users/something else that makes them say "this place used to not suck" that they're receptive to the idea of a "pure" new community.
3) Start sending PMs around and hope you don't get banned for spam before you get a decent sized userbase on your new forum.
4) Watch your new forum die on the vine because elitist asses circle jerking each other do not a good community make.
5) Come crawling back to the old forum, older and wiser.