can somebody tell me how to prepare fo upsc peliminary and which city one should go to prepare for it ???

There are lot many coaching centres like RAU's,e.tc. which one can choose,cities where one can get good coaching institutes are delhi,allahabad,kanpur,e.tc.But one can even prepare at their own city at any good institute.

Write your location where do you come from.where do you live

You can even prepare prlims from home during your under grad.But better you consult the near by coaching IAS institute.Delhi is the best place for civils studies.