CTRL-b, " - Split window horizontally (i.e. split and add a pane below).
CTRL-b, % - Split window vertically (i.e. split and add a pane to the right).
CTRL-b, UpArrow - Move to the pane above (I prefer to rebind this to CTRL-b, k to be similar to Vim).
CTRL-b, DownArrow - Move to the pane below (I prefer to rebind this to CTRL-b, j to be similar to Vim).
CTRL-b, LeftArrow - Move to the pane to the left (I prefer to rebind this to CTRL-b, h to be similar to Vim).
CTRL-b, RightArrow - Move to the pane to the right (I prefer to rebind this to CTRL-b, l to be similar to Vim).
CTRL-b, z - Toggle maximization of current pane.
CTRL-b, ESC, 2 - Resize all panes to equal size.
CTRL-b, { - Swap current pane and pane to the left
CTRL-b, } - Swap current pane and pane to the rigth
CTRL-b, SPACE - Toggle between layouts
CTRL-b, q - Show pane numbers.
CTRL-b, x - Kill current pane.
CTRL-b, c - Create a new window.
CTRL-b, n - Switch to next window.
CTRL-b, p - Switch to previous window.
CTRL-b, 3 - Switch to window 3.
tmux new - Create and attach to a new session.
tmux new -s NAME_HERE - Create and attach to a new session named NAME_HERE.
CTRL-b, d - Detach (i.e. exit) from the currently-opened tmux session (alternatively, tmux detach). Note, this means press and hold CTRL, press b, release both, press d.
tmux ls - Show list of tmux sessions.
tmux kill-server - Kill all tmux sessions.
tmux a - Attach to the previously-opened tmux session.
tmux a -t NAME_HERE - Attach to the tmux session named NAME_HERE.
CTRL-d - Delete (i.e. kill) currently-opened tmux session (alternatively tmux kill-session).
CTRL-b, [ - Enter copy mode, and enable scrolling in currently-opened tmux session. Press q to exit.
CTRL-b, CTRL-b, COMMAND - Send the command to a nested tmux session (repeat prefix for each level of nesting).