i can try to post quality post and my post will be quality link resource. but first question: how to find them easily, yes, i can search power by vbulletin and check if they are forums and if pr of homepage is high. but it is slow and time costing, any better? thanks.
Use seo quake ( fire fox add on that shows PR for results from google searches ) . Even a high PR forum has does not have all high PR pages
Or better yet don't focus on PR - look at how active the forum is and whether or not it's relevant to your site's topic. I don't post on forums to get links; I post on forums to interact with others of similar interests, which can in turn have this nice side effect of bringing plenty of targeted traffic, especially if I become visible as an authority figure or trusted forum member (a pillar of the forum community, so to speak). Try it, you just might like it.