From the research question to matching every claim with the right type of evidence.
Define the question first
Molecular identity, analytical performance and biological activity are different questions. Defining the question before searching prevents collection of sources that are interesting but do not answer it.
Distinguish source type
A primary study reports original data, a systematic review synthesises studies, and regulatory guidance describes principles or expectations. No category answers every question. Preprints and unreviewed summaries require clear labelling.
No claim broader than its source
Every statement should stay within the model, population and endpoint examined by its source. In vitro or animal data do not become human guidance. Date, corrections and conflicts of interest are part of the evaluation.