Economists, having long labored to create mathematical tools that describe how hyper-rational people behave, might have devised an excellent means of modeling future computer superintelligences. This guide explains the uses, assumptions, and limitations of utility functions in the hope of becoming a valuable resource to artificial general intelligence (AGI) theorists. The guide will critique the AGI literature on instrumental convergence which theorizes that for many types of utility functions an AGI would have similar intermediate goals. The guide considers the orthogonality thesis, which holds that increasing an AGI's intelligence does not shrink the set of utility functions it could have. This guide explores utility functions that might arise in an AGI but usually do not in economic research, such as those with instability, always increasing marginal utility, extremely high or low discount rates, those that can be self-modified, or those with preferences that violate one of the assumptions of the von Neumann-Morgenstern utility theorem. The guide considers the possibility that extraterrestrials have developed computer superintelligences that have converged on utility functions consistent with the Fermi paradox. Finally, the plausibility of an AGI getting its values from human utility functions, even given the challenge that humans have divergent preferences, is explored.