I take a very relaxed approach to it, I keep a good handle on sanitation and fermentation temp, and pitch a good amount of healthy yeast, so I'm not worried about stuck ferments. So once I don't see any more airlock activity, I'll usually give it another week or so to clean up whatever it's gonna do before bottling.
+1. I usually plan on about 3 weeks total from pitching to packaging.
To elaborate on Spider's commend on "cleaning up things", yeast will naturally produce things like diacetyl (tastes buttery) and acetaldehyde (green apple) during fermentation. If you take the beer off the yeast immediately after fermentation is done, these flavors will stay in your beer. However, if you give the yeast a little time after you reach terminal gravity (a few days to a week), it will reduce these compounds.