The Official Gmail Blog reminds us how to quickly work through email by keyboard alone:
I find a message that looks important or interesting, and open it using the enter key. If I need to reply, I hit r. Reply all? That’s a. Once my response is ready to go, tab + enter sends it on its way. Back to my inbox with g + i. More navigating around with j and k, selecting with enter. Archiving (y) and replying (r). Starring some stuff for later (s). The occasional forward (f). Sending with tab + enter.
I delete a lot of messages after reading — especially those from mailing lists — but Delete isn’t mentioned here. To delete use the