Are your ducks in a row?

This is my writing quote for the day (week? month?), which I found somewhere, and keep above my desk… but I’m afraid I can no longer remember where it came from, so I apologise for the lack of an attribution...

So you want brilliant dialogue?

Make sure it’s the only dialogue your character can possibly say given who he or she is, where he or she is and to whom he or she is saying it. Then make sure you have all your ducks in a row – every event leading up to the dialogue should be believable and every event after the dialogue should be at least partly the result of the dialogue. Finally, make sure we care about the character, so that we’ve got a vested interest in what he or she is saying, and in the results of what he or she says.