Halide perovskites are an intriguing class of materials that have recently attracted considerable attention for use as the active layer in thin film optoelectronic devices, including thin-film transistors, light-emitting devices, and solar cells. The "soft" nature of these materials, as characterized by their low formation energy and Young's modulus, and high thermal expansion coefficients, not only enables thin films to be fabricated via low-temperature deposition methods but also presents rich opportunities for manipulating film formation. This comprehensive review explores how the unique chemistry of these materials can be exploited to tailor film growth processes and highlights the connections between processing methods and the resulting film characteristics. The discussion focuses principally on methylammonium lead iodide (CH3NH3PbI3 or MAPbI3), which serves as a useful and well-studied model system for examining the unique attributes of halide perovskites, but various other important members of this family are also considered. The resulting film properties are discussed in the context of the characteristics necessary for achieving high-performance optoelectronic devices and accurate measurement of physical properties.