Black holes are undoubtedly the most fascinating and exciting objects in the Universe, capturing the imagination of scientists and film writers alike. It has been a long standing objective of the scientific community to understand how these objects work and whether the black holes seen in the centers of galaxies, including our own, show analogous physics to those seen in stellar mass binary systems in other parts of the galaxy. In this body of work I aim to introduce the reader to the many broad facets of the subject to which the first 4 chapters are dedicated. These explain the mechanisms allowing black holes to be seen, i.e. luminous accretion and reprocessing of radiation, the environments black holes are found in and the effect this can have on observations. The 5 chapters following the introduction are the papers that I have published from my studies in this field as I try to address the outstanding problems which present obstacles to our understanding of unified black hole accretion. I hope that you, the reader will find this work compelling in nature and an enjoyable insight into one of the greatest mysteries of the Universe.