PHOTOGRAPHS BY JAY BOERSMA

Lay vs. Lie

This one's easy. In most cases:

Lay requires an object

You always lay something (or someone, if that makes it easier for you to remember.)

You don't
lay down on the bed
but you do
lay your head down on the pillow.

You do
lie down on the bed
but you don't
lie your head down on the pillow.

(You can also lie about the object of the word lay but that use is a whole other story.)