Fourteen leading manufacturers of microcontrollers are analyzed, with consideration of bits, series and families of devices. The main characteristics and requirements for the practical application of microcontrollers for both embedded systems and for training and design are highlighted. The reasons for the widespread use of AVR microcontrollers by the community for training and familiarization with programming are revealed. The possibilities of hardware resources and the advantages of using a set of series of models of the STM32 microcontroller group in embedded systems are analyzed. The reasonability of using ESP32 microcontrollers to build components of Internet of Things (IoT) and systems with Internet access is established. A comparison of the hardware resources of microcontrollers of three manufacturers is performed, considering available program memory, the number of peripheral interfaces, ports and pins. The procedure of decision-making for selecting microcontroller is proposed and examples of application for proposed procedure are described.