Here are some ways people go about in creating backlinks.
One of the quickest way to create backlinks is to create several (not on the same site but different sites) Social Networks accounts. Keep in mind that these sites now use the nofollow tags on their pages and often encrypt the outgoing links. If you have an online community, you are encourage to use CAPTCHA during registration and monitor multiple accounts using the same IP Address.
You Are Leaving Pages
Some sites (usually government owned) utilize a “You are Leaving” page and if you look carefully at the URL, you can see that substituting your domain, name for the landing page listed, it creates a backlink to your site’s homepage. Since this page is just created and unknown, a link has to be created to that exploited page so it can be found by Search Engines thus making it a valid backlink. If you have such technology on your site for exit links, you will want to make sure that the robots.txt file and meta tags encourage Search Engines to ignore them so it will not be abused.