My .tmux.conf file template. You can try this as your .tmux.conf file after backing up yours. The configuration file is located in ~/.tmux.conf.

.tmux.conf

# scrollback size
set -g history-limit 10000

############
# Keybinds #
############

# Changing ctrl+b to ctrl+a as the command button
unbind C-b
set -g prefix C-a

# Pass through xterm keys
set -g xterm-keys on

# Redraw the client (if interrupted by wall, etc)
bind R refresh-client

# Reload tmux config with ctrl+a+r
unbind r
bind r \
    source-file ~/.tmux.conf \;\
        display 'Reloaded tmux config.'

# Vertical splits with g or C-g
unbind g
unbind C-g
bind-key g split-window -h
bind-key C-g split-window -h

# Horizontal splits with v or C-h
unbind h
unbind C-h
bind-key h split-window 
bind-key C-h split-window

# Using the mouse to switch panes.
set -g mouse on

# Ctrl - t or t new window
unbind t
unbind C-t
bind-key t new-window
bind-key C-t new-window

# Ctrl + w or w to kill panes
unbind w
unbind C-w
bind-key w kill-pane
bind-key C-w kill-pane