One of the biggest improvements in my tmux productivity came when I changed my prefix (default Ctrl + b) to backtick (i.e. to `) I am a heavy user of tmux and spend a lot of time switching panes, switching windows, entering visual mode, detatching etc. so this really feels faster.
# change prefix to backtick
unbind-key C-b
set-option -g prefix `
bind-key ` send-prefix