1. In a system of national currencies, the Deutschmark exchange rate would appreciate or be revalued against other currencies. Not possible, since there is no Deutschmark anymore. Thoughts of Germany leaving the euro are purely hypothetical. That is a political no-fly zone.
2. Germany could boost domestic household consumption. Germans would spend more on products and services from France, Italy, Spain, Greece, etc. That makes sense. However, how to do it? One bad idea is to decree a general pay rise by law. Should that happen, German manufacturers would likely shift yet another portion of their production to the auxiliary economies of Germany: Poland, Czech Republic, Slovakia.
3. Increase budget spending. This is what Brussels is recommending to Berlin - "to do more to boost infrastructure spending." Brussels always loves more spending. Bad idea: as though Germany didn't have enough highway or airports. In addition, it is unclear how building more unnecessary infrastructure would cut Germany's trade surplus.
4. Germany could increase the domestic consumption by cutting income taxes. This is a market-compatible solution, which the German households would certainly welcome. Berlin, however, is uneasy about the possible shortfall in budget revenue. (And, by the way, cutting income tax rate would make German workforce even more competitive.)
5. Germany could cut her contributions to the EU common budget, which netted about EUR 11 billion in 2011 alone. However, this is a political taboo, again.
Well. It's not easy to be THAT successful. What would you do if you were in Chancellor Merkel's shoes?