Quickest way to turn existing XHTML 1.x pages into HTML5?

Quickest way to turn existing XHTML 1.x pages into HTML5?

I'm having problems with programming HTML5.
I am a self-taught web developer learning HTML5 for a re-launch of a
client's website.
What is the quickest way to take the current XHTML 1.x pages and make them
HTML5?
Plus, can I still use XHTML 1 validators?