When hitchhiking it is good to know at least a few phrases of the language of the place where you are, or of your potential drivers. See Tips for hitchhiking for more about hitchhiking in general, and Wikitravel:List of phrasebooks for more extensive vocabularies. Here are seven key phrases which will come in handy:
Don't bother to try asking in Danish, Swedish, Norwegian or Finnish. Almost all local people speak English, and will be confused when you try to speak their language - and if you do speak it at a reasonable level, you won't need this phrasebook.
Russian is probably the most important language to learn, many older people speak or at least understand Russian, especially when their mother tongue is a Slavic language. A lot of young people understand at least a bit of English (of course more in the (big) cities than in the countryside). German could also be very useful (it is (was?) very used for the commercial exchanges).
2. Otivate li do ...?
3. Moga li da patuvam s vas?
4. Shte me ostavite li na purvata benzinostancia (= would you drop me off at a first gasstation?) 5. Moga li da sliaza tuk?
6. Blagodaria za patuvaneto!
7. Iztok, Zapad, Sever, Jug
Southern Europe/South America
Some knowledge of basic Japanese is near-essential to Hitchhiking in Japan.
While driving with young people, using English is more advisable and understood widely. Russian is widely spoken as well. On main inter-city roads there are special stops for hitchhikers, designed for soldiers to hitchhike easily (until the government forbade soldiers from hitchhiking, for safety reasons); use them if possible.