Enteral nutritional support plays a major role in the management of patients who are critically ill in intensive care units (ICU), those with poor volitional intake, persons with chronic neurological or mechanical dysphagia, and individuals with gut dysfunction. Part I of this review will briefly discuss the principles governing nasoenteral feeding and will describe in detail the endoscopic-assisted methods for placing enteral feeding tubes. These include percutaneous endoscopic gastrostomy, jejunal extension through a percutaneous endoscopic gastrostomy or direct endoscopic jejunostomy, and the "one-step button". In addition, the types of enteral food with focus on disease-specific enteral diets will be discussed. Finally, the latest innovations in enteral feeding including immune-enhancing nutrients such as arginine, omega-3 fatty acids, glutamine, and nucleotides advocated for critically ill patients will be discussed. Questions regarding possible complications and long-term results of the various methods of enteral feeding will be discussed separately in part II.