Before embarking on your systematic search, you'll want to define your research topic in an easily searchable way. This involves separating out the key concepts of your research question. There are various tools to help you do this. One of the most commonly used in systematic reviews is PICO; for scoping reviews, PCC:
These worksheets can help you formulate a searchable question.
Some journals publish systematic or scoping review protocols. You may also register your protocol in PROSPERO or Open Science Framework.