Do you need to find quick answers to a clinical question for a specific case? Or are you beginning a systematic review? This will determine what type of search will suit your purposes best.
Define your research question clearly
You will run into difficulties if your question is too narrow (no results) or too broad (too many results). A clear and concise question will help you find that balance that is just right.
Think about what types of results you need
Are you hoping to find a guideline or meta-analysis of the literature on a question? Or do you want double-blinded randomized controlled trials? Knowing what you hope to see will help you use the best search terms and filters, and it will also help you recognize it when you see it.