Looking for that handy readout at the bottom of every Finder window telling you how many items are in the active folder, and how much free space is on your hard drive? In OS X 10.7 Lion, it's turned off by default (part of the cleaner, scrollbar-free new UI style). Easy enough to restore it, though: just choose Show Status Bar (⌘-/) from the View menu, and continue on with your fully-informed computing day.
More Lion tips coming all week long!
Apple OS X Yosemite