Some good references about setting this up in a decent way. I won’t copy my rcfile here yet, but I’m basically using this one.
You can reload your conf file with ctrl-b and then :source-file ~/.tmux.conf, or in the shell tmux source-file ~/.tmux.conf.
# enable powerline
run-shell 'powerline-config tmux setup'
# vi keybindings
set-window-option -g mode-keys vi
# Set 256 color terminal
set -g default-terminal "screen-256color"
# split panes using | and -
bind | split-window -h
bind - split-window -v
unbind '"'
unbind %
# reload config file (change file location to your the tmux.conf you want to use)
bind r source-file ~/.tmux.conf
# switch panes using Alt-arrow without prefix
bind -n M-Left select-pane -L
bind -n M-Right select-pane -R
bind -n M-Up select-pane -U
bind -n M-Down select-pane -D
# Enable mouse mode (tmux 2.1 and above)
set -g mouse on
# don't rename windows automatically
set-option -g allow-rename off
######################
### DESIGN CHANGES ###
######################
# loud or quiet?
set -g visual-activity off
set -g visual-bell off
set -g visual-silence off
setw -g monitor-activity off
set -g bell-action none
# modes
setw -g clock-mode-colour colour5
setw -g mode-style 'fg=colour1 bg=colour18 bold'
# panes
set -g pane-border-style 'fg=colour19 bg=colour0'
set -g pane-active-border-style 'bg=colour0 fg=colour9'
# statusbar
set -g status-position bottom
set -g status-justify left
set -g status-style 'bg=colour18 fg=colour137 dim'
set -g status-left ''
set -g status-right '#[fg=colour233,bg=colour19] %d/%m #[fg=colour233,bg=colour8] %H:%M:%S '
set -g status-right-length 50
set -g status-left-length 20
setw -g window-status-current-style 'fg=colour1 bg=colour19 bold'
setw -g window-status-current-format ' #I#[fg=colour249]:#[fg=colour255]#W#[fg=colour249]#F '
setw -g window-status-style 'fg=colour9 bg=colour18'
setw -g window-status-format ' #I#[fg=colour237]:#[fg=colour250]#W#[fg=colour244]#F '
setw -g window-status-bell-style 'fg=colour255 bg=colour1 bold'
# messages
set -g message-style 'fg=colour232 bg=colour16 bold'