Which Word When, part II

I was asked about the following pairs of words, so I thought I would post my response.

which/that
Imagine “by the way” following every “which.” "The 2008 campaign season, which [by the way] started too early, will be over Nov. 4, 2008." The “which” phrase adds a useful, but not necessary, piece of information. So, if “by the way” makes sense, use “which.” Also, if the phrase needs a comma, you probably want to use “which.” Here’s a poetic reminder from Patricia T. O’Conner, former New York Times Book Review editor: “Commas, which cut out the fat, go with which, never with that!”

compliment/complement
To compliment is to praise or admire; to complement is to round out or bring to completion. “She complimented her son on his athletic prowess and hoped it would complement his application to Vassar.”

fewer/less
If you can actually count it, use “fewer,” as in “there are fewer eggs today than yesterday.” But if something is uncountable, like time, boredom, or love, use “less,” as in “it took less time to get home,” “I was less bored than usual,” and “I love you less than ever!”

flesh/flush
I have an English Springer Spaniel (named Bailey), a gundog whose traditional job is to flush out game from hiding – in other words, to chase from its hiding place. To flesh out (or add details to) what I mean, a well-trained Springer (in other words, not Bailey) would know to move in a zigzag pattern in front of the hunter seeking game birds.