I’ve been doing this quite a bit lately, and didn’t even realize it was a new thing until I did it in front of a friend the other day, and she said, “Woah! I didn’t know you could do that!” So, forgive me if you already know this, but give it a shot if you didn’t.
Ever try and browse through the default Open File window? The icons can be super small, especially in List View. If your eyes aren’t up to the task of figuring out just which Picture.jpg you’re looking to upload to Facebook, then give Quicklook a try.
There’s really not that much more to it. When opening a file in any app, like Word or Pages or even Safari and Chrome, click on the file you want to see, and hit the Spacebar on your Mac keyboard and the document will zoom up into a much more readable size, just like it does in the Finder.
Slick, huh? Hit the Spacebar again to zoom back out, and resume your Open File process. Boom!
Via: Macworld Hints