Tmux cheatsheet in 21 lines

# Sessions        # seperate instances of Tmux
tmux ls         # Lists sessions on cmdline
tmux new-session# Create a new session (aka instance of tmux)
tmux attach -t5 # Attach to session 5
Ctrl-b $        # Rename current session

# Windows         # hidden windows, like tabs
Ctrl-b c        # Create new Window
Ctrl-b ,        # Rename current window
Ctrl-b w        # List windows
Ctrl-b l        # Open last window
Ctrl-b f        # find by name and cmd history

# Panes           # split-screen windows
Ctrl-b "        # Create new Horizontal Pane
Ctrl-b %        # Create new Vertical Pane
Ctrl-B arrowkey # Switch active Pane
Ctrl-b [space]  # Rearrage panes
Ctrl-b {        # Reorder panes
Ctrl-b z        # Zoom (full screen) active pane
Ctrl-b pageup   # Scroll back, ctrl-c to end

This page has a chart for screen users making the switch to Tmux