This paper illustrates our approach to research-based teaching strategies, including their evaluation. It deals with a teaching sequence on the superposition of electric fields, implemented at college level in an institutional framework subject to severe constraints. The general approach to the teaching-learning processes is that of a motivated and guided construction. Consistently, this sequence was designed on the basis of two interrelated studies: a content analysis of the domain and an investigation of common ways of reasoning. Thus, the part played by multicausality in the superposition principle and the tendencies previously observed in common reasoning as regards the analysis of multivariable problems inspired the main choices made for this sequence. The evaluation method, using 'conceptual profiles', will be explained and illustrated with the main findings. A discussion of this approach ends the paper.