There is a lot of drinking in the Game of Thrones series. Whether your personal tastes run more toward a Tyroshi Pear Brandy or pure water fresh melted from The Wall is more your speed, there is one thing that holds true. If you set that chalice down on a family heirloom (and darn near everything in one of the castles is a family heirloom), the lady of the house is going to make sure you're sorry. You may not even realize you've done anything. And you wouldn't like how they exact revenge in Westeros.
Be safe and carry with you one of these Game of Thrones Wax Seal Coasters. Each depicts sigil of one of the houses of Stark, Lannister, Targaryen, Baratheon, Greyjoy, and Tyrell. Better yet, carry the whole set of 6 along with you so that you can be sure to pull one out of a house that's on friendly terms with your hosts at the time. It could be the difference between winning and dying.