In Safari 3 (and earlier versions of the browser), you could use the Up Arrow (or Down Arrow) key to quickly move the cursor to the start (or end) of the Google search box — this made it really easy to add terms to either end of something you’d already typed. In Safari 4 Beta, however, the Up and Down Arrow keys have been repurposed — now they scroll through the suggested matches for your Google search terms.
As it turns out, you can still jump around the Google search box — and nearly any other text field in nearly any program on your Mac — using the keyboard. All you need to do is add the Command key to the Up (or Down) Arrow key, and you’ll jump to the start (or end) of the Google search box. These are OS X-standard cursor control keys, and they should work in most any application (exceptions include Microsoft Office 2004 and 2008) that involves text.
But as long as you’re learning keyboard editing shortcuts, you should know there are many others. Press and hold the Option key and the Up or Down Arrow, for instance, to move up (or down) through your document, one paragraph at a time. Command and the Left or Right Arrow will jump to the beginning (or end) of a line; Option and Left or Right Arrow will jump backward (or forward) one word at a time. You can add the Shift key to these shortcuts as well–Shift-Option-Up Arrow, for instance, will select multiple paragraphs in your document, starting at the cursor position and moving upwards.
These aren’t the only keyboard-based editing keys out there, either. In many applications, you can also use Emacs’ editing keys to move (and perform simple edits). On the linked page, stick to the commands that begin with C-, which is shorthand for the Control key. Further, only the movement and editing keys will work, not some of the more esoteric commands. For instance, try Control-T in the midst of a word in the Google search box, and you’ll see the two adjacent characters swap positions. Control-A moves to the beginning of a line, Control-E to the end, and Control-K will erase everything from the current cursor position to the end of the line. (If you’re going to experiment with these shortcuts, I suggest doing so in TextEdit with a document that you don’t care about. That way, you can learn without fear of destroying a key document.)
I’m sure there are other cursor movement shortcuts out there; feel free to share if you’re aware of any I’ve left out. Thanks to Mac OS X Hints reader DarthMagnus for the tip on the Command plus Arrow Key shortcuts.