The Basics

The Command Character: Control+b (C-b)
C-b ?: list-keys
C-b :: command-prompt
C-b [0-9]: switch to window 0-9
C-b c: create a new window
C-b d: detach session
C-b l: last window
C-b n: switch to next window
C-b p: switch to previous window
C-b s: choose-session
C-b w: choose-window
C-b [: copy-mode
C-b ]: paste-buffer
C-b M: monitor window for changes
C-b , s: rename window to "s"