While forums can be a powerful tool to make affiliate sales or simply have links pointing to your site, you should be pretty careful on how you process as moderators are usually prompt to ban spammers from their forums.
Here are a few tips to successfully use forums to promote your website and affiliate programs:
- Find forums that match your website and affiliate programs' niches
- Attach a signature including your link to all your posts
- Present your website in your profile
- Ask and answer questions
- Build relationships with other forums members
- Post useful information
Do not post links that look like spam in your actual posts. Wait instead for a couple of months, until you're done with all the previous steps and have built a good reputation in the forum. Establish yourself as an authority and then make a honest recommendation about your affiliate offer or ask for some feedback about your website.