In Gmail, go to Settings (under the gear icon) and under the General tab find the section that says "Keyboard Shortcuts". Set them to "on".
With keyboard shortcuts activated, when you return to your inbox you will see a blue line next to the first email. This indicates that the email is currently "highlighted". With the email highlighted, you can now do some shortcuts.
- Highlight next email:
up/down arrow
- Select email:
x
- Open selected email:
enter
- Archive selected email:
e
- Delete selected email:
shift + #
- Reply:
r
- Forward:
f
- Archive:
e
- Go to inbox:
left arrow
thenenter