Tmux cheatsheet

Config file ~/.tmux.conf, place it on every machine you use tmux on.
The first two lines are must-haves, the rest are nice to have

set -g mouse on
set -g history-limit 50000

set -g base-index 1
setw -g pane-base-index 1
set -g renumber-windows on
set -g focus-events on
set -g set-titles on
set -g set-titles-string "#I: #W"

Cheatsheet:

tmux - start a new session
tmux ls - see your sessions
tmux a -t 0 - jump into session 0

Inside tmux, every command starts with hitting Ctrl+b (let it go) and a key:

c - make a window
0, 1, 2 - hop between windows
w - show windows so you can pick one
s - show sessions so you can pick one
d - detach the session
" - split the window into two panes, top and bottom
% - split the window into two panes, side by side
z - blow up the current pane to fill the screen
arrows - move between panes

Click between panes with your mouse.
To close a pane, window, or session, I just hit Ctrl+d — same as in any terminal, not just tmux.