Social bookmarking is one of the best sources of getting traffic in a site. For this reason, it is considered one of the main sources for link building.
How to do social bookmarking?
First find a social bookmarking site.
Create an account (you need an email address for creating an account in social bookmarking site)
After creating account, a confirmation link will be sent to your email, you have to go to your mail and click to that confirmation link for account confirmation.
After link confirmation, you can login with password to your social bookmarking account.
When you enter into a social bookmarking account, you will find step by step guideline (just spend some time into account, you will understand what you have to do to create a links with your designated URL)
Here are some top page ranked social bookmarking sites list: