My initial tip would be to change the colour of the forum to make it stand out from the crowd
There are a great number of skins and modifications you can make
Is there a welcome message you can add to your site so that unregistered users are offered an
incentive to register and participate?
Re: Gaining members in a short time
Have you thought about leafleting your local builders merchants? (or engaging the services of the greasy spoon vendors who sell bacon butties to the masses) to get the message across?