When to start a new paragraph

I get this question all the time. When do I start a new paragraph? As someone who never took writing classes or went to university for creative writing, it was a struggle for me to learn this. When I stumbled across this amazing Tumblr post on Pinterest, my world changed. I printed this post and kept it beside my desk while I wrote my first book. Feel free to do the same! 

 * If you are the one who created this post way back when, please comment as I would love to give you credit for all the help you've given me!