The best way to find your User ID number is to mouse over your profile picture. You will see the number at the end of the URL at the bottom of your browser (I use Chrome). It looks like the figure to your right.
Use the Facebook App
A MUCH EASIER way to find your Facebook user ID number and be able to COPY the text, is to use this tiny little Facebook App called, “whats-is-my-user-id”. It’s simple. While logged in go to this link http://apps.facebook.com/what-is-my-user-id