Use filters to limit your search quickly. Filters appear to the left of your search results and include Article types and Publication date, among others, with even more under Additional filters.
Once you have one good article, click Related Citations to see more like it.
Use clinical queries to limit to clinical research areas. Clinical Queries are available under PubMed Tools on the homepage. Search by keyword and then refine results among three categories: Clinical Studies Systematic Reviews and Medical Genetics.
PubMed is very smart and uses automatic term mapping to recognize thousands of concepts and map them to an appropriate term. Use keywords in your searches, but leave out words like the, of, or and also do not use punctuation (like quotation marks).