Let's return to our Cook. First we'll feed him some weak dialogue, then add some technique to it.
An Example of Weak Dialogue
You walk up to the Cook.
COOK: I heard the Captain wants to see you.
True, you know you need to seek out the Captain, perhaps to get your next mission, but the dialogue is amateur.
Approach that Cook again.
COOK: Captain says go see him so he can kill you.
COOK: Captain's been by four times. Looking for you.
Or, after you've done something heroic:
COOK (in an admiring tone): Captain's says go see him. Pick up a medal or two.
Again, you notice that keeping better dialogue short is tough when it needs to provide the double function of prompting action and staying interesting.
These are the kinds of tradeoffs the game writer must weigh. In a game, short dialogue is almost always preferable to longer pieces of dialogue.