We report on the first steps of KETTI, a project that aims towards the development of a competence model for undergraduate teaching assistants (UTAs) in computer science. Using qualitative methods, we obtained a classification of existing designs for teaching that employ UTAs; some of the observed factors directly influence the methodological decision space of UTAs. We developed and implemented a UTA training scheme designed to foster student-oriented teaching in recitation sessions along with an instrument to gauge the effects of this instruction on a variety of psychometric scales. We report results from a small-scale pilot study at three institutions showing positive effects on teaching-related beliefs and self-efficacy.