The high season for visiting Berlin starts in May and ends in October. During this period, prices for everything from accommodation to souvenirs skyrocket, so if you are looking to save, it is better to visit in low season. Rates for apartments in Berlin drop in proportion to the number of people wanting to stay in them, but bear in mind: winters in Berlin are cold, and many entertainment venues have holiday hours or close for low season. Berlin is worth visiting for festivals and exhibitions, but accommodation should be booked in advance.
Citizens of United States and Canada, as well as EU members, do not require a visa to go to Berlin, if they intend to stay for less than 90 days for recreational purposes (tourism). Citizens of other countries should inquire about the necessity of having a visa prior to travelling to Germany.