SEO stand on two pillars, the first is on page SEO that mean optimizing your web-pages to search engines through tags, web-page structure and content. The second pillar is off-page optimization that is mostly about getting more and more backlinks.
The most popular and common back links strategies are:
Article marketing that allow you to write article and publish them on other websites, and having one or two links from the resource box (that is the about the author box)that points back to your pages. Article marketing is the best most effective back links strategy that can get some good backlinks to your website, but to do it effectively you need to consider building links to most of your pages not only the home page, and using the right anchor text (the text that links to your page) when linking.
The second great backlinks strategy is through blogging and blog posts. This strategy have three options, the first one is to run your own blogs and publish unique related content in your blogs and link from the blog link, the blog posts to your pages; you can have a free blogs (there are few free blogs providers online like word-press and Google). The second option is to post blog posts as a guest; some bloggers are accepting guest blogging to have more unique content published on their blogs. For this strategy you need to search for some related blogs as individual or look for some networks of blogs that accept guest blogging. The third option is the most popular because it's easy, it's blog commenting and it's simply performed through searching some related blog posts that allow commenting on the post and submitting a comment there, you can add your name and link to the comment.
The third backlink strategy is to get backlinks from social media sites; sites like social networks allow you to link from your profile page, from your wall posing and sharing content. Other sites like bookmarking sites allow you to post only links with description and title. Other social media sites are video sharing and here you can get backlinks from the description of your video. My favorite social media sites are the micro blogging that allow you to share some small tips and ideas and links. The popular macro blogging site is twitter.
Social media allow you to increase your traffic rapidly if used correctly, for example with face book you can generate hundreds of hits daily if reach a lot of friends and shared high value content on your blog, group and fan page. Then always post some helpful valuable tips to your friends and they will follow.
Other great back links strategy that also can be a traffic generation strategy is forum posting, but you need to be involved on a related and high traffic forums. New small forums are great for good backlinks, but popular forum can also generate traffic in good quality and quantity.
A good other back links strategy is through link exchange, two way and three ways. But because it's a time consuming its better be focused on good value partners who will add to your page authority and traffic. So carefully chose your partners, but do not waste your time on the popular and high page rank sites. All of them will not even respond to their e-mails. And they will never exchange with new website or low page rank websites.
There are more sophisticated back links strategies that also can bring you high quality links, but they require some effort from your side. Like creating a software or tool then submitting your PAD file to software directories. Or creating a good word-press theme or website template share and it for free on the template directories. You can also publish a short e-book or repost and submit it to book directories.
Either link building strategy you choose to use you need to follow ethic rolls, do not ever spam other website, do not share worthless content and do not publish any link farms on your site. Do not use any adult only content and do not get any links from adult sites and link farm or pages that allow spam.
Here are some great references I strongly recommend
