Low emittance electron beams are increasingly important in scientific researchthrough their use in for example Ultrafast Electron Diffraction (UED) and Mi- croscopy (UEM), as well as through their use in high energy light sources such as Free Electron Lasers (FELs) and Inverse Compton Scattering (ICS) light sources, whose applications extend beyond scientific research to medical and industrial applications. In each of these applications, transverse beam emittance is an im- portant figure of merit, with a lower transverse emittance improving the efficiency and resolution of any given application. In UED and UEM, the transverse emit- tance determines the momentum and spatial resolution, in FELs lower transverse emittances lead to lower gain lengths and greater laser energies, and in ICS the emittance directly impacts the efficiency of high energy photon production. Thus minimizing the electron beam emittance is desirable in these applications. The emittance is limited by the initial emittance, but can be effectively degraded by intrabeam and beamline element forces and by both fast and slow machine state drift. The initial transverse emittance is partially determined by the initial trans- verse beam size. This dissertation discusses emittance optimization studies for beamlines designed for UED and ICS, the development of photoelectron sources with spatially dependent photoemission for generating beams with small transverse dimensions, and the implementation of systems for improving the resolution and mitigating sources of noise in a UED beamline.