It is called re-search! It means you should have done the search first. As obvious as it is, many researchers do not put enough effort on search and the main reason is that researchers are doing research and usually there is no searcher in the team.
In systematic reviews, the search methods are part of the research methods. It means that the search methods should be reproducible and if anyone runs the search methods he/she should be able to replicate the search results.
If you have a research question or a draft protocol/proposal, it is the right time to run the searches BUT the questions are:
Where to search?
- Databases, Google, Grey (Gray) Literature [Free Grey Literature slides]?
What to search?
- There are several methods to collect the keywords and concepts for your search.
How to search?
- Search strategies usually consists of
When to search?
- Recording the search date alongside the search strategies makes it possible to repeat the search and get the same or similar results. Remembering replicating the results and reproducing and research!