Comments on forums / blogs - write comments on forums / blogs on relevant subjects and indicate a link to your site - This is a great way to build links to your site and a great way to connect with potential customers.
Active forums and blogs can be very effective if it is a popular forum or blog, this service has three major advantages: traffic, SEO and branding.
Specifically, about SEO, it is important to note that in most forums and blogs is now defined as No follow links. Although it has been said before that Google follows No follow links, it still does not mean that the force will pass to your website.
This is a huge potential traffic that forums. If the forum is active and popular in his field, it can bring you many visitors to your site.