The course provides conceptual grounding and practical tools necessary to tackle the issue of sample size determination from a variety of perspectives and considering different research designs. Building upon the main concepts of power analysis, the course will deal with common and advanced designs, including hands-on demonstrations of dedicated software, modules, and approaches. The emphasis will be on what to do concretely and will present a toolbox of conceptually and practically useful ways to deal with the issues. Dedicated software will be presented with an eye on practical use in a range of research scenarios. The course will cover Bayesian approach to sample size determination and simulation-based methods to estimate power in complex or non-standard designs. Through lectures and practical sessions, the course aims to equip participants with some of the skills needed to determine sample sizes transparently and convincingly in grant proposals, preregistrations, and publications.