Make sure you try currywurst in Germany. It's basically a hot dog with tomato sauce (ketchup) and curry powder. Tastes brilliant and only costs 1 or 2 Euro.
If you have a high-def video camera, be sure to take it on a hike with you to the bottom of the canyon. HD is the only way to bring out the gorgeous contrast of blue sky and red rock that you'll want to show everyone at home.
I went on two tours alone...I made life-long friends along the way! That's the nature of Contiki.