Amazon makes it extremely easy to create one of these. All that's necessary is having a book or books available through Amazon. But be warned: it gets tricky when it comes to out of print titles, titles with limited availability, anthologies you're in that don't have your name listed among the authors, books by you published under a different name, etc. In most cases Amazon won't let you add these, which is why my Author Page looks a little sparse.
That's also why I created "The Ostensible Nicholas Kaufmann Library" Listmania list. It's much more complete in terms of titles.
One really fun thing about Amazon Author Pages is that there's a "Customers Also Bought Items By" list on the right hand side of the page that shows what other authors customers look up at the same time they look me up! A few surprises there, and a few names that aren't.