The Autoptimize (I hate trying to spell that) plugin is a HTML/CSS/JS minification and caching plugin. Easy setup, and quick configurations. Be sure to enable the advanced settings if you’re having any troubles with wonky-ness on your website after enabling some of the settings. There may be another box you need to check in order to get it working again.

This plugin is also the approved plugin for minification on hosts such as WPEngine.