I prefer to use an available shortener URL provider (such as Bitly, etc.) rather than to install shortener URL app.
From shortener URL provider, you have to setup only a A/CNAME Record (for your custom domain) to make your own shortener URL. No hassle & it is using their server resources (not our server resources).
Or if that shortener URL will be used only for your site & your site has a fixed ID system for its pages, you can setup simple shortener URL using .htaccess file.
For example:
You have a blog/site using WordPress at domain: blog.example.com
& your shortener URL domain at: sho.rt
On sho.rt domain, you create a .htaccess file:
RedirectMatch permanent ^/([0-9]+)$ http://blog.example.com/?p=$1
Then, from:
http://sho.rt/xxx
will be redirected to:
http://blog.example.com/?p=xxx (your WP posts/pages)
Of course by this way, it won’t has other features such as stats, etc. for your shortener URL.