Until now I had been using Get Info the hard way, open and close for each file, but recently, I noticed by accident that by not closing the "Get Info" window and just clicking on a drive, a file, folder, or an application ... I noticed that the information was updated on the fly.
I'm sure this is old news to some but for me it saves a few key strokes and was a nice touch. :-)
[Editor's note: The one-window Get Info interface has both pros and cons ... this tip is the "pro" side; the "con" side is that it's very hard to compare more than two files at once. If you have just two, it's pretty easy to click back and forth and note the difference. If you have three, it's just tedious. Personally, I'm hoping for an option for multiple Get Info windows at some point in the future]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010815115707963