netherlands, germany, etc. march 2012

Hi! I’d please like advice on the cheapest, most efficient way to travel between the countries/cities listed in my trip itinerary (zurich to bruges to groningan to berlin to frankfurt to kassel to zurich). i have accommodations with family/friends in all the listed cities except bruges and zurich, so any advice on cheap (but nice and SAFE) hostels/hotels in those cities would also be wonderful! also, any advice on MUST SEE sites in and around the cities in my itinerary would also be helpful. we are first time visitors to all these cities! thanks for your help! cheers

Train will be most efficient for all of this, although bus may be cheaper.