To get more quality traffic, have you ever suggested your friends to your forum? I have not. None of my friends would be interested into this kind of stuff because none of them are interested in computers that I know of. But, would you suggest your friends to you forum? I would if I knew of friends that were into computers and the type of stuff I am. You never know, they just may be into forums as much or more than you.
Do you think posting in forums is bad ? I believe that shows one's effort to learn, share ideas, gather to improve, etc. I would definitely suggest my friends if i had any :'-( I'm kidding. Of course I would to all of those who are into this field.
I have the same problem as you, none of my friends would be interested in a webmaster forum. I maainly promote my forum in signitures in other forums.
I don't think that asking your friends (computers freak or not) to go on the forums / site you've owned is a good way to get traffic. The snowball effect is better with social bookmarking and others techniques with virtuals friends .
Most of my friends are computer illiterate but still mange to understand how forums work. I got many friends on my forums based on the subject. Easiest way to promote a forum IMO.