You've made the right decision (for once) and decided to call a cab instead of brave the old one-eye closed serpentine in your own ride. Good choice. Now for the tough part. Where do you live? Whip one of these babies out, give your friend a sharpie and you're as good as home.
Pro player tip: When in NYC at 3am, simply writing "The Hilton" will not suffice and proper use of the alcohol by volume glass can prevent the situation all together.
In contrast, proper use of the 2 beer bong can lead to napkin necessity.