The most useful phrases I learned to say in German:
"Ich spreche kine Deutsch. Sprechen zie Englisch, Franzosisch, oder Spanisch?"
Ironically, while I speak and read several Romance languages, and a smattering of several more obscure languages, I do not speak or read German, which constitutes a large part of my heritage. This book, in conjunction with a German-English dictionary, helped me communicate with those few Germans who don't speak English, Spanish, or French on my one trip to Germany.