Determine your destination in Germany. The typical tourist destinations include Berlin, Munich, Dusseldorf, Frankfurt, Bonn or Cologne.
Go to the Deutsche Bahn website and enter "London" to "Berlin." Select your preferred time and date; click "Search." Review the options offered and book online.
Visit the websites of high-speed passenger train Eurostar. Review the times, dates and prices for journeys from London to Brussels. From Brussels -- transfer to the Thalys, or the Inter-City Express high-speed train to Cologne -- which takes just under two hours. Book your ticket online at Eurostar's and ICE's websites.
Take the high-speed ICE train from Cologne, to reach any destination in Germany. Review times, dates and fares on Deutsche Bahn's website.