The development and application of new test systems and test methods is central to the progress of in vitro toxicology. In order to live up to the future challenges, it is important to use the vast knowledge of adjoining fields, such as cell biology or developmental biology, and to attract specialists from such areas to develop new methods. Not all of them bring with them the necessary experience and training required for the development of toxicological test systems. Thus, promising new biological test systems sometimes still require additional considerations to become successful. Sometimes even the referees of scientific journals and their editors seem to lack judgement guidelines for minimum performance standards. Here we provide a list of points to be considered for the establishment of a test method. The chapters range from the explanation of the meaning of positive controls, performance standards or signal-noise ratios to a discussion of statistical considerations, suitable solvents and data display formats. The considerations are simple and expressed in a non-mathematical format, with a strong focus on plausibility and common sense. The major intention of this article is to provide a compilation of important issues requiring consideration. Whether they apply to a specific system and whether action is required must be determined by individual judgement.