Laboratory education makes up an extensive part of natural science education at universities. To support meaningful learning during laboratory work, students should prepare by carefully studying the protocols. The aim of this study was to design and evaluate a preparative learning material that focuses on protocol steps with the design goal to help students to (i) understand the "why" (reason or theory) of protocol steps, (ii) make practical choices, and (iii) do troubleshooting. To reach this goal, protocol steps have been enriched with theoretical, practical, troubleshooting, and/or calculation questions to form interactive protocols. This design process resulted in a list of design choices (i.e., when to include a question and how to design a question) and a showcase of questions in the interactive protocols. These interactive protocols were implemented and evaluated in a real educational setting. From the evaluation results, it was concluded that the interactive protocols were successful in preparing students for the laboratory work. After the laboratory work, students reported a more diverse and slightly less positive contribution of the interactive protocols to their understanding of the protocol steps and their ability to make practical choices. A significant difference was found in the perceived usefulness of the troubleshooting questions before versus after the laboratory work, which is suggested as a topic for further investigation.