Close your email software and the Gmail tab in your browser (YES, no email, I mean it).
Disable all kinds of email notifications - browser extensions, system tray notifiers etc. Close all IM software as well.
Close you Twitter client (if any). Along with any other social media notifiers. Close that Twitter & Facebook browser tabs as well. An "I won't use it anyway" promise is just fooling yourself. Even that "(1)" number appearing next to the tab title - like "Facebook (1)" - will distract you. And you know it.
Set your cell phone to ring after 8-9 seconds only. And no text-message sound.
Put on the headphones with your favorite music, that gets you into "the zone".