Well-conducted systematic reviews are invaluable for synthesising research findings. The conclusions of a review depend on how the research question was formulated, how relevant studies were found and how studies were selected for synthesis. Here, we present a practical guide for ecologists and evolutionary biologists on formulating a question for a systematic review, and finding a representative sample of research findings. We explain the steps involved using a worked example and practical training exercises. Throughout this guide we share tricks of the trade, included rules of thumb and software that we have found useful. We hope our paper helps demystify the systematic search process and encourages more researchers to adopt a systematic and reproducible approach when searching the literature.