I find myself in this kind of situation a lot. I'll be photographing someone who doesn't have a whole lot of modeling experience, but they want me to take photos of them (ie, a friend while on vacation, engagement photos, etc).

I say these things now:

• Stand with one foot in front of the other, to slim the profile
• For a man, squat and look up, to avoid double chins (apparently, not a flattering pose for a woman)
• In bright sunlight, close eyes and then open on the count of 3 to avoid squint
• For a couple, have the man hold the woman from behind
• For a couple, have them touch foreheads (and then wait to see where they go from there, usually works pretty well once they get over the giggles)

I think I need more in my bag of tricks to guide these models around. What are some of your best model guidance tricks?