Instead of doing follow bookmarking, the best link building is guest posting. It's a more quality link. You must be careful to do link building, as the Google algorithm nowadays is really sensitive to detect manual action link building. If ou read the guideline from the Google Webmaster Tools, Google will send your links to their sandbox index if the spider finds your site has so many low-quality backlinks overall. You should avoid dofollow bookmarking, as my own research, most of the dofollow bookmarking sites get bad impact towards the sites that are listed on them. I removed all my links from dofollow bookmarking sites. Try do guest posting.
Indeed, guest posting is hard to do, as we need to pass the admin moderation. But once you get approved, and you have dofollow backlink within your post, you'll get better rank on the search engines. Simply, read the Google Webmaster Guidelines. That's all you need to know about how to earn backlinks.