Sign in to your GMail account at http://www.gmail.com.
Click on the gear icon near the top-right corner and click on ‘Configure inbox’:
In the Select tabs to enable’ popup, uncheck all the boxes next to “social”, “promotions”, “updates” and “forums” and click “Save”
You can re-enable the GMail inbox tabs anytime you want.
How To Enable GMail Promotional Tab and Other GMail Tabs
Go to “Settings’ > “Configure inbox” and check the boxes next to the Gmail tabs you want to activate.
Hit “Save” when you are done.