I have a number of forums websites, mostly niche-topic forums but also a few broader topics.
They are actually complete social/business networking sites based on my own custom codebase, but for the purposes of this post I'll refer to them as forums.
I've been doing this for about 9 years and my oldest forums have decent, though not amazing, traffic and rankings. The income they generate is almost entirely from adsense. I think that my sites are a great free resource and the ones that are actually in use by a lot of people are very well-liked by their users, who frequently express their thanks to me for building the sites. However despite being very useful, popular sites they are not getting much recognition from the search engines.
I'm also trying to start several new forums in new topic areas to help supplement my dwindling income. Promoting a new forum is difficult because of the lack of content, though in the past I've been able to overcome this by emailing other webmasters within the same niche, and asking for a link swap. Although I'm not entirely convinced that link trades are dead (provided it's done over time with similar-topic sites), I am very sick of doing it and I'd like to redesign my promotion strategy from the ground up.
There seem to be volumes of info on what you shouldn't do, but very little about what one SHOULD do to gain rankings. I am aware of linkbaiting but I find the idea unappealing and contrived, especially in light of all the crappy made-for-linkbait articles that I've come across recently. I got into this business because I enjoy writing code and providing useful resources to people, not because I want to write blog articles. It's not that I'm completely unwilling to try it, but it seems like there must be a better way to get people using these forums, and to improve the rankings of my established ones.
So I'm looking for any white-hat ideas that actually make sense for promoting a new forum/community site. Also, any tips on de-sandboxing my newer forums would also be appreciated. Thanks in advance.