Identify the print jobs in the queue
If you double-click a print job in a printer's queue, it will open a Quick Look window showing the printing preview of that job. Especially useful when the file names don't have descriptive titles.
[crarko adds: I tested this, and it works as described. Simple, fun, and I would not have guessed to try this.]
Source: http://feeds.macosxhints.com/click.phdo?i=04128c017a47491b8e4820a67aef0eda