Content should be fresh and informative. Content should be informative so that people get the answers of the questions they have. Also try to get the quality backlinks from the site.
In my opinion Use DoFollow forum sites for posting and always use fresh content. Read forum rules in each and every sites and follow them. Give suitable and meaningful answers in forum posting. I think it will help you.
Hi, Your postings should be natural and fresh and don't spam follow forum rules choose suitable or relevant threads to answer. Definatly it will help you get backlinks and increase in SERP results.
Sharing your valuable comment to the forum is the best way to get high quality backlinks and then you will gain a lot of visitors or traffic to your site. You must select high pr forum too.