Shop 'til you drop

You could ruin a good set of heels window-shopping in Berlin.
Stroll Kurfürstendamm, particularly between Uhlandstr. and Adenauerpl., for Versace, Jil Sander, Gucci, and Sonia Rykiel. If you're looking for something other than the same old same old, follow Berliners to the boutiques of Annette Peterman and Nanna Kuckuck on Bleibtreustr.
With the exception of Berlin's proudest department store, Kaufhaus des Westens (KaDeWe, 'Department store of the west'), Tauentzienstr. is lined with mass market retail stores. KaDeWe has an excellent selection of foods as well as a vast array of services, from umbrella repair to tailoring.
Mitte's credit card trail is Friedrichstr., between Unter den Linden and Stadtmitte. Tank-size Bentleys and costly ounces of French perfume now define the street where Soviets and Americans faced off in the Cold War. The Friedrichstadtpassagen and Galeries Lafayette (with a fascinating interior and gourmet basement) are the main emporiums. Mitte's maze of streets around Weinmeisterstr. is where to find what's driving the under-thirty crowd into debt. Half-sewn shirts are the new prêt-a-portier.
Kreuzberg, where the protesting students of 1968 have grown grey alongside Turkish immigrants, has two main shopping streets. Between bars and take-out eateries on Oranienstr. are bookstores, wool specialists, ethnic grocers, internet cafés and Luzifer, a long-time maker of monotone linen and wool clothing. Bergmannstr. is less scruffy but still full of funky gift and household supply stores, as well as a few clothing stores.
Full of people under thirty, Prenzlauer Berg is where to watch the trends. Kastanianallee and Szredzkistr. are two streets to comb, but you're likely to find an interesting window display wherever you walk.