This chapter examines in detail the necessary practical skills needed to facilitate the development and sustainability of ELISAs. Basic methodologies to set up all systems are discussed so that the reader can both investigate the possibilities of tests using his or her reagents and use with confidence the reagents obtained from other sources. As with all other tests, it is vital that scientists realize the principles of the methods to allow good judgement based on quantifiable and controllable features. In other words, there should be a full understanding of what is being performed in the laboratory. The intention of this training is to produce new skills and understanding as well as to encourage critical assessment. Such a mentality is necessary and supported through the application of statistical criteria to results and to continuous monitoring of performance.