As you probably know, OS X uses an 'expanding' Save dialog -- it defaults to a compact size, but once expanded in a given app (by clicking the triangle to the right side of the window), it stays that way in that particular program. This feature carries over into 10.5 (if you prefer always-expanded Save dialogs, use this hint, which still works in 10.5), but it's now been joined by its friend, the expanding Print dialog.

Like the Save dialog, the Print dialog defaults to small in every app, until you expand it. This state is then remembered the next time you use that app. Using this fact, it was pretty easy to find out the key to changing it in every app -- I just set it in one program, then looked at that program's preferences to see what had changed. That bit of work led me to the PMPrintingExpandedStateForPrint key; it's a boolean set to NO by default, and to YES in an app where you've expanded the Print dialog.

Therefore, to get the expanded Print dialog by default, use one of these two Terminal commands. To affect just your own user, use this one:

defaults write -g PMPrintingExpandedStateForPrint -bool TRUE

To set this preference for all users, use this version (requires admin privileges):

defaults write /Library/Preferences/.GlobalPreferences PMPrintingExpandedStateForPrint -bool TRUE

From now on, every app will use the large Print dialog by default -- with the exception of any program where you might have used the Print dialog and quit with it in the small state; you'll have to set those manually. (And yes, I searched the queue before running this, to make sure I wasn't stealing someone's spot in the contest.)