I think forums are ideal for promoting anything, but they are also about the discussion model at first. "People got the power". And they should be honest and reliable. I.e. you should not leave just positive opinions, but also criticism, if it's grounded and based on facts, not just emotions coming from untrusted source. Also, the format you choose is not truly important - but so is the proper marketing.
Also, each forum should be moderated. Moderation is the basic principle of providing clean and expertised information. Of course, you as admin should be an expert #1 in the area your forums are about, the same about each Moderator you may have.