State Estimator technology has been in use in Control Centers for over 3 decades. It is still a challenge to support the State Estimator (SE) 24 x 7 due to its critical role in ensuring Grid reliability and in supporting operational decision-making tools in real-time, more so due to the extensive penetration of renewables. Due to its scope and complexity, it is still perplexing to many who are involved in supporting the tool. The tutorial provides several key aspects including the criticality of SE, the extent of network model choice of detail, solution quality, tuning, and 24 x 7 support system all of them in a nutshell. This tutorial provides a basic understanding of State Estimator as used in the industry, its criticality in control centers in operating the grid reliably and provides insights into industry practices to support 24 x 7 and provides the challenges due to renewable penetration. This tutorial is taught by industry practitioners beginning as frontline engineers and managing the technology over years of experience. The tutorial is suitable for students, engineers, managers, and researchers to provide support and practical solutions.