I don't know. I think forum posting is not a new method in seo. If you wants to succeed as SEO you have to give your best practice in Search engine optimization as well as you need to remain about relevancy in your work.
I suggest try out articles submission and social media marketing as that could prove to be a good media for marketing through SEO. SEO has become such an important part that even well reputed firms today are opting for this sort of marketing strategy. I think updating the website at regular intervals could also prove to be a good option.
Off-page SEO is all about getting other site to vote for your site via a form of backlinks, facebook likes, tweeted, reviews, bookmarked and so on. if you get a lot of votes to your site or page, Google will give you a higher ranking.