First, grab a soft measuring tape—the kind you’d find in a sewing kit. No tape? No problem. Use a string and then measure that string against a ruler. Just don’t use a metal ruler; your skin will not appreciate the attitude.
You’ll also need a mirror (for those contortionist moves) and a notepad. And yes, you can do this solo, but having a friend helps. Just make sure they’re not the type who laughs at your “pinch an inch” dance.