Pshaw, it was easy because you're legally obligated to get a copy.
As soon as I jump out of the eye doc chair I ask for my script for glasses AND my script for contacts!
Some docs will be reluctant to give it to you because of the HUGE profit margins on glasses (my dad used to be in this business, on the computer programming end of it) and it's scary how much profit can be made sometimes - so I have no qualms about it at all!
In fact, I have a few little cards full of my scripts and I keep track of them to see how my eyes change - and I've got my eyes tested overseas (free with a pair of glasses in HK that were super fab and super cheap) and have that script too! LOL.