SEO is most popular way to increase your sites popularity over the different search engines, It includes so many techniques such as,

Link wheel,
Link trundle,
Blog commenting,
Forum Discussion,
Press release.

There are so many ways to increase traffic and here are some of them which could help you,

Article Submission
Forum Posting
Press Release
Blog Submission.

Here are some tips of seo which could bring lots of traffic to your site,
Directory Submission
Dofollow Blog Submission
Article Submission
Press Release
Forum Posting with signature link.

There are so many benefits of seo and here are some of them,

Targeted Traffic,
High ROI,
Keeps content fresh & unique,
Cross-Browser Compatibility,
Instills confidence in prospects.