Content and links are the building blocks of all Internet marketing and they're inter-related. Without content there's nothing to link to, and without links there's less opportunity for content to be found and seen. These two blocks fit together in a complementary way. Good content will find a receptive environment for links, and the more links you get, the more valuable your content becomes. External links to your content not only contribute to direct traffic, but they are also an important factor in how search engines rank your content.
Don't buy links! Don't take take shortcuts in link building. There are companies that will offer to provide lots of links to your site for a fee. Search engines look down on this practice and may even punish some sites when they confirm that external links have been purchased. Better to slowly build up links by genuinely asking other website owners and bloggers to link to your site.
Generally speaking, if you've done a good job with the first building block, content, you'll have a fairly easy time asking others to link to it. After all, if the content is indeed helpful, compelling, and relevant to the other website, there is no reason for them not to link to it. If, however, the content is not very compelling, why should they bother? Quality of content will have a direct relationship with the number of links you can get, so always focus on the content first! For example, suppose you're a pet sitter and you post a video showing how to train a dog to fetch a newspaper. Pet oriented Bloggers would usually be happy to either write a blog post about such a video or add a link to the page.
Requesting bloggers to blog about your content can lead to great traffic and strong links. But there are other ways you can build up links. You can add them to other sites yourself. Commenting IN AN APPROPRIATE WAY on blogs, adding links back to your site within your comments, is perfectly acceptable and welcome, as long as it is on topic and adds to the subject of the post.
I'll give another pet sitter example since I'll be speaking to pet sitters next week and have some examples handy for them. Dogster and Catster are two online social forums that welcome community content, interaction, linking and participation. Pet owners ask lots of questions, and if you were a pet sitter that had content that answered some of these questions, posting a comment with a link to your page would be appreciated by the community. Of course there are a rapidly growing number of such social forums and social media sites for just about every area of interest. Finding appropriate venues for linking is not that hard.
The more you participate, the more your traffic will grow and the more external links you'll have.