In my opinion:
-You need a good design in order to catch the attention of a viewer and also to show that you put time into the forum
-The content is a must. Try adding some update section to your forum (like w2.isohunt.com) having this update section will show the viewers your devotion to the forum and will help them know what is going on
-Moderation for a over 18 site would not be as much needed but you still need to moderated to make sure there is no unwanted material on your forum.

-Idk if i wanted it to look professional for some reason I would put my pic on the home page saying your current owner/moderator or something haha or somewhere on the page