Priority Inbox is a great feature for GMail. Even so, some might prefer to not have it enabled

1. Click on the gear icon in the upper right corner of Gmail's main interface to open the and click on Settings from the dropdown menu
   

From there, go to the Priority Inbox page by clicking on the Priority Inboxlink

At the Priority Inbox page, you can disable it by selecting the Do not show Priority Inbox radio button, and clicking the Save changes button