The present state of the methods commonly used for characterization of the phase, mineral, and chemical composition of fly ashes from coal-fired power stations is described and summarized. The application of various methods is briefly discussed; these methods include macroscopic observations, ashing procedures (high-temperature and low-temperature), physical separations (density, magnetic, particle size, froth flotation, and electrostatic), chemical leaching, sequential physical and chemical treatments, as well as optical microscopy (reflected and transmitted), electron microscopy (scanning and transmission), X-ray diffractometry, differential thermal and thermogravimetric analyses, Mossbauer and infrared spectroscopy, and different chemical analyses. A short critical overview on the advantages and limitations is given, as well as certain recommendations during application of the above-listed methods. Some considerations about the practical use of data for fly ash composition are also present.