This chapter provides several examples of early activation of a critical attitude during a discussion of questionable explanations. One concerns the use of the survival blanket to protect against the cold, a theme which leads to discussion of a compromise between two imperatives: that of returning as much energy as possible to oneself (by putting the silver side towards oneself), and that of emitting as little energy as possible towards the outside. There is a preconceived notion that turning the most reflective side inwards would be enough to retain heat. Among other findings (no "expert anaesthesia", many "delayed critiques"), one of the interviewees quickly questioned this initial idea by "putting together" what little she knew. This example and two others (osmosis and capillary rise) suggest that the secret early critiques lies in the effort to gather information without waiting for all of it. A discussion on how to help teachers and educators avoid "delayed critique" and "expert anaesthesia" introduces the issue of teacher preparation. [For the complete volume, "Developing Critical Thinking in Physics: The Apprenticeship of Critique. Contributions from Science Education Research. Volume 7," see ED615688.]