How do I join a page?

How do I become a fan of a page?  Facebook answers the question of join and become a fan of a page in the Causes Help Center.   Their answer:

If you see a Page that interests you – on a friend’s profile, in a News Feed, or when using the Pages Directory  – you can click on the link to that Page to learn more about it. Once on the Page, you can click the "Become a Fan" button (see below), to become a fan.

Example To become a fan of the page "How Do I Facebook": Do nothing until you read steps 2-4. Click on the "Find us on Facebook" button (below) to go to our page on Facebook. Look for the "Become a Fan" button on the actual page (see example below) and click it. Now you are a fan.  It's that simple. click here when you're ready button looks like this but has no border This is what our page looks like on Facebook. This is a snapshot, not the actual page.

NOTE:  Can't find the "Become a Fan" button?  Where did it go?  The Become a Fan button will disappear once you become a fan of the page (click here to read more about that situation).