Prepare before diving into a database. Brainstorm for terms that you can use in searching. Keep in mind that the first word that pops into your head may not be the only one, or the term used by professionals. For example, is it "healthcare" or "medical care"? Is one broader in meaning than the other? What is it about medical care that you want to focus on? Use the subject terms/thesaurus of the database you are using (if available). You may discover terms you hadn't thought of on your own.
Use specific search terms. Words can have different meanings in different disciplines. A portfolio in the business world is not the same thing as a portfolio in the art world or the education system. Combine words like this with another search term to narrow down your results.
Limit the number of words you use in a search. Too many terms can result in a search with no results. You will rarely need to use more than three search terms. Avoid words such as the, of, a, an, etc. Most databases and search engines ignore them.
Use advanced search options. You can reduce irrelevant results by controlling what field the term is found in (title, abstract, subject) and how the terms are related (AND gives you documents that contain both terms, OR gives you all documents that have at least one of your terms, NOT excludes documents that have irrelevant terms). If you have procrastinated and need full text "right now!" use the limit options that will give you only results that are available in full text within the database. But be aware that you miss a lot of good material this way.
Once you find a relevant article, look at the subject terms attached to it and the terminology used in the abstract to see if there are terms that you hadn't thought of that can result in a better search. Look at the bibliography of the article. Are there works cited that you should add to your research?
Broaden your definition of what is relevant. Don't reject articles just on the basis of the title; take the time to read the abstract. Consider articles that have a different perspective than your own. True learning happens when all ideas and perspectives are considered, analyzed and synthesized. You should read far more than you cite in you final project. Expect to examine four times as many sources as you end up using.
Focus on being sophisticated, rather than speedy. The more time you put into your research, the more you will understand your topic.