Although technology has improved out of all recognition since the introduction of large ground-based telescopes, the observing process has only changed in that the astronomers have been removed from the telescope dome to an adjacent control room. Increasing budgetary pressures are requiring facilities to operate as efficiently as possible and this means ensuring that the best science programmes are completed in a timely manner, preferably within a single semester. Where variable weather parameters have a significant effect on the success of the proposed observations, then matching the scientific requirements to the pertaining weather becomes a necessity. There are a number of ways by which this can be achieved. This paper reviews these new modes of observing and address the challenges of implementing them.