How can I get sleepy enough to take a nap?

I mean, in the middle of the day. I need to take a nap to catch up on sleep, and please don’t tell me another way of catching up on sleep, I am just interested on how I can get sleepy enough to take a nap in the middle of the day.

Sometimes I can and sometimes I can’t but I want to make sure I do tomorow. I was thinking maybe reading for an hour straight to fall asleep?