You can go quite a long way with gestures and smiles, especially if accompanied with thank-yous, excuse-mes and greetings.
I agree with Metal about money- it is very important. Last year, I was living in Cambodia, where they use the dollar alongside the riel, and it was very confusing to pay in dollars and get change in riels, etc. A few basic phrases for essential transaction, like 'how much' help people settle in.
Also, prepare them for the fact that not all gesture and smile stuff works. Prepare them to terminate such a conversation politely.
