Before you start searching it may be a good idea to consider what scope your search is to have.
Would you like the search to generate fewer but hopefully relevant hits? In that case you should do a narrow search with few search words. The disadvantage could be that you risk missing literature where the author has not expressed him-/herself in the way you do, whereas the advantage is that you don’t have to go through a great number of hits.
If you instead want to be assured that you don’t miss relevant articles you should do a wide search with a lot of different search words, i.e. variants of words describing the terms you’re looking for. You’ll get a greater amount of hits to go through, but will not risk missing as many possibly relevant studies.