Berlin's food scene has come on leaps and bounds in the last few years. It's not quite a foodie destination like Paris, London or New York is but you can really enjoy a gamut of dining experiences from cheap, tasty falafels and currywurst to Michelin-starred delights.
There are some great places to sample German cuisine. Dressler, Lutter & Wegner, Vau and Zur Letzen Instanz all serve up tasty national dishes from various regions (and at varying prices), though of course there are plenty of 'lecker' bratwurst and the like to be found on the streets.
In general the eating scene is more international though. The large Turkish population ensures there are plenty of cheap kebabs and falafel spots dotted all over the city, and you'll also find excellent Asian spots and very good mid-high end French, Italian and Fusion places.
If you're a foodie travelling on a budget, try the lunchtime deals at places like Weinbar Rutz, Vau and other expensive places.
Don't be afraid to ask for an English menu - most decent establishments should have one or will happily translate for you.
Note that a service charge is ususally included in café and restaurant bills, but it's still normal to leave a small tip (1-2 euro per head) or at least round it up to the nearest euro if you're satisfied with the food and service.