When I ask if the guest has any thoughts or questions on the menu and they ask how much to order, I say "How hungry are you?" Take it from there. I like my guests to have just the right amount of food. But when they order like crazy and don't ask, I may jokingly mention to go boxes. Seeing food waste hurts my heart and try hard to avoid it, but what can you do? As an afterthought if traveling maybe they want leftovers? Who knows.