The POINT-AGAPE collaboration, an international project looking for gravitational microlensing towards the Andromeda galaxy, uses the 'superpixel' technique to detect MAssive Compact Halo Objects (MACHOs). The 3-year survey has discovered about a dozen microlensing candidates. Part I of the thesis describes the project's background. Dark matter is discussed (cliapter 1). Microlensing is explained, emphasising the POINT-AGAPE work, and the superpixel technique is introduced (chapter 2). CCD technology and the Isaac Newton Telescope are discussed (chapter 3). In Part II the three recent POINT-AGAPE pipelines and their results are detailed, including the work at Queen Mary. The elimination of Mira variables is discussed, these masquerade as microlensing events (chapters 4 - 6). In addition we estimate the efficiency of detecting microlensing events (chapter 7). Part III describes various methodological issues associated with thesuperpixel technique, which uses a program called SExtractor to detect lightcurves with a bump. However, this generates fake lightcurves associated with CCD defects, bad pixels and resolved stars. Likelihood maps are investigated (chapter 8). The bad pixels and resolved stars were masked, but no mask is perfect and it is important to understand the degree of incompleteness. CCD defects are studied, their causes and effects are analysed; as are bright variable objects (chapter 9). In particular, a new method is described, involving close pairs of variables, which can be used in analysing the defects (chapter 10). Tight groups of variables are studied and bad columns analysed (chapter 11). Telescope pointing is investigated, relating offsets with defects and analysing anomalies in the bad columns. Field close pairs are discussed; once defective pairs are accounted for, what remains are genuine close pairs (chapter 12). Part IV discusses a search made for Cepheids (chapter 13) and summarises a coauthored paper on Nova discoveries in M31 (chapter 14). This is followed with appendicies with some more technical details. collaboration, an international project looking for gravitational microlensing towards the Andromeda galaxy, uses the 'superpixel' technique to detect MAssive Compact Halo Objects (MACHOs). The 3-year survey has discovered about a dozen microlensing candidates.