To get started, try registering in a popular social bookmarking site like StumbleUpon and get a feel of the interface. These sites can evolve significantly so it is best to explore what the site currently offers. Like any other social networking site, you should fill up your profile because people might check it out if they find that you share good links. After that, share as many favorite bookmarks as you can even if you do not manage these sites. Even though social bookmarking is a common place for advertising, it is always good to show to others that you want to share cool sites too alongside advertising.
Since you want others to focus more on the site you wish to advertise, you should complement the link with a good bookmark description. If you already set a description on your website, the social bookmarking site may detect it automatically. Otherwise, you should give a clear and concise description of the bookmark so others know what to expect. If you have experience in search engine optimization, try to optimize the description by inserting a keyword or two so the description is better indexed by the search engines. You can also do the same with tags. Adding multiple tags is encouraged as long as you keep the associated tags relevant to your bookmark. Adding random words can increase exposure but people may dismiss your link as spam.
Once you get the feel of one social bookmarking service, expand what you have learned to other sites. Even if the bookmarking site isn't very popular, what matters is that you have that area covered. As long as the social bookmarking site allows links to be made available for public viewing, the site should have some potential in attracting new visitors.