Shortcut-hungry in Gmail? Try this: Shift + ?
Viola! You will get a shortcut cheat sheet on top of your inbox or whatever you’ve loaded up into your account.
Note though, you have to enable shortcuts in your Gmail settings. To do that, pop into your settings panel > General > Keyboard shortcuts. Or, after you press Shift +? , you can see a note on the upper part that your shortcuts are disabled, click on the ‘Enable’ option.
Check out the video: