Biding My Time

This is a lot later than I thought I'd have my first math related post. This is the first of many.

Consider a 100 storey building, each floor has a balcony. You have 2 marbles, and you are trying to determine the highest floor from which you can drop a marble without it breaking. What strategy would you use to minimize the number of trial drops you have to make to determine this height? Using that strategy what is the most number of drops you would have to make to determine the floor in the worst case?