From SEO point of view forum submission is very important as it can produce really quality links. Some of the advantages of Forum Submission are
a) Highly relevant: As usually forums are dedicated to a particular topic, its content is highly specific. For example if I am promoting a garage the car forums would be the best. When crawlers parses the forum and finds a link there it will be highly relevant.
b) Dynamic: Forums are highly dynamic as new threads and posts keep on populating on a regular basis. So robots will index them more frequently.
c) Anchor text: Though one my promote same anchor text again and again, however content keeps on changing adding uniqueness to the context. Uniqueness is core of all search engines when it comes to avoid any spamming practices.
Despite all above mentioned facts, to get quality links from forum is very tough. Some practical problems I found while promoting websites through forums are
a) Most of the forums do not allow links in the posts and often user account of advertiser's are banned permanently.
b) Some forums allow signatures to be added, however links are not allowed. Even if links are allowed most often they are made ineffective with "no follow" attribute.
c) Signatures are generally stored at separate file and editing signature for different anchor texts changes signature at all posts. So one forum is generally good to promote only one keyword or phrase.
d) It takes time to earn links from forum as one can't add link to each and every posts. It looks very unnatural and highly disliked by forum owners. So forum is not a good idea to earn quick links.
e)Forums are less in number as compared to directories, bookmarking, article, blogs etc sites. So advertisers are strictly sniffed out.
Looking above scenarios I would like to ask what kind of strategies you adopt while promoting websites through forum so that your user account is not banned and quality links keeps on coming. Please share your views specially forum experts are highly revered to contribute with their pioneering ideas.