When selecting a forum for investing my time, some of the things I look for are: 1) PR value of the host domain 2) Recent activity and relevant discussions 3) NoFollow vs. DoFollow signature files 4) Quality of posts What and how do you determine this things quickly? Is there are search tool that helps you see these things in one view?
I first look at the quality of the post, just spend some time on browsing the website, then will get idea whether it is good to join
Quality of the posts and how many active user base it has must be considered first. That is why I like Digital Point.
I think not any tool to give you all quick results (at a glance) to all your points. For selecting a good forum it need some concentration to look at the forums manually. By spending little bit time to analyse different HQ forums give you better results.
I don't think there's a fast way to evaluate how good a site is. Spending some time on it by posting and surfing the boards will help you on your evaluation -- you will see how informative it is, how active the community is, etc.