Astronomers require large amounts of spectroscopic data for faint astronomical sources if they are to successfully confront today's most important cosmological and astrophysica1 problems. However, until recently such data has been particularly difficult to acquire and the supply of telescope time available has fallen well short of demand. This thesis describes spectroscopic techniques of high efficiency that allow the data to be obtained using a minimum of telescope time. The technical aspects discussed include instrumentation, observing practices and data reduction. In particular, a new faint object spectrograph for the La Palma Observatory and an automated multi-fibre spectrograph coupler for the Anglo-Australian Telescope are described. It is now feasible for extensive spectroscopic surveys to be carried out at very faint magnitudes.