Last fall I posted about trying the Sticker Shield. It's a clear plastic backing that is *supposed* to adhere to the inside of the windshield like a Post-It note. You'd put the sticker on the shield, then put the shield on your window.
Well, I finally used it with my new parking sticker when I visited last weekend, and I don't recommend the Shield. I thought it would peel on and off the inside of the windshield easily, but it was stuck hard to the glass after only a few hours. I'll have to scrape the Shield off and then it won't re-adhere.
Sanddunerider's suggestion for laminating the sticker and hanging it from your rearview mirror is a great idea.
The Shield also caused a little issue with the parking lot attendant. He was confused when I declined to let him put the sticker directly onto the windshield, then annoyed, then downright rude. I literally had to block him (twice!) from reaching in and slapping the sticker directly onto the glass, even after explaining the Shield to him. SDC really needs to go with a 'hanger' pass instead of a sticker, if only to keep the peace.