I hope this helps!
ICE (Inter City Express) trains often need reservations (about 4.50 Euro per person).
If you have reservations but a train is late, get evidence of sorts (aka keep the paper with your reservation on it) so if you miss subsequent trains, you can get a refund.
Download and regularly update the Eurail app.
Download the City Maps 2 Go app.
Use airbnb instead of a hostel at some point--it's a very popular way to stay in someone's else's property for cheap (airbnb.com).
Know where your hostel/airbnb is and how to get there from the train station or airport.
If you don't know who the obnoxious American is in your group, it's probably you. So then just embrace it because then it's more fun.
Don't stress about missing trains. And don't be afraid to look into every option in order to get somewhere! IC buses (connected with Deutsche Bahn, which works with your Eurail pass), flights...anything. A little persistence goes a long way.
Heidelberg Altstadt is a great train station for going short distances. We had to use it to visit our friend in the hospital when she broke her arm.
Always plan on rain. Even if it doesn't, an umbrella isn't that big.
Plans will fail; don't sweat it. Always have a backup.
Even though Ryanair is cheap, the airport is really far and pretty expensive.
Patience. Things are not always going to go your way. Go with the flow. Love the person in front of you (from today's house church message).
Be humble. Sometimes the stereotypical loud American tourist that you swore you would never be count not describe your group more perfectly. Embrace it.
The yellow departure (Abfahrt in German) sheet at the train station is your best friend, and there's always another train so don't fret!
Always have at least your Eurail and wallet and passports with you at all times.
People in the group have traveled to these places so far (plus some I'm sure I don't know about):
Black Forest/Berlin/Triberg/Wuerzburg/Rothenberg/Hamburg/Munich/Stuttgart, Germany
Lake Bled, Slovenia
Majorca (aka Mallorca), Spain
Canary Islands, Spain
Vatican City, Italy
Vienna, Austria (our EFT....Students should go on their own if it isn't their EFT next year)
St. Petersburg, Russia
Prague, Czech Republic