How do people who recently bought a Macbook Pro get the free upgrade to Lion?
The Lion up to date program is public. It currently says the deadline to ask for a free copy is August 19, 2011 and macs purchased on or after June 6, 2011 are eligible.

Otherwise, Mac OS X 10.7 Lion will cost you $29.99, and is available on the Mac App Store (link). You can also go to an Apple store to download it (if you have a slow connection), and Apple will be making a version on a USB thumb drive available for $70. (More info here.)