The recent development of NBIC technologies has led to the emergence of new techniques that allow the modification of genetic, morphological, and physiological aspects of the human being to improve their capacities. In light of this situation, the eternal debate continues: is everything technically possible ethically acceptable? To answer this question, an ethical reflection is needed to assess the scope of enhancement techniques and to direct them to the service of human progress and the common good. Many authors have already begun this reflection, opting for a case-by-case evaluation. However, there is a great lack of specificity in the definition of the criteria that would allow an ethical analysis of each technique, in order to determine the licitness of its application. In response to this need, a practical guide for the ethical assessment of not only human enhancement techniques, but of any intervention on the human body is proposed. This guide is based on the four principles of personalist bioethics proposed by Sgreccia: the principle of defense of physical human life, the principle of totality or the therapeutic principle, the principle of freedom and responsibility, and the principle of sociability and subsidiarity. These principles are the common thread of some questionnaires that serve as support in discerning the licitness of a technique, by virtue of the overall good of the person in their three-dimensional structure: body, mind and spirit, and the respect for their inalienable dignity.