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 relevant one or the term used by professionals in the subject area. For example, is it Healthcare or Medical care? Is there a significant difference between the two. 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 happen across terms you hadn't thought of on your own.
Consider the specificity of your terms. Words can have different meanings in different disciplines. Portfolio in the business world is not the same as portfolio in the art world or the education system. It would be important to combine "portfolio" with another search term that would narrow it down to a specific discipline or application of the word.
Limit the number of words you use in a search. Too many terms can result in a search that is so specific that it produces no results. As a general rule of thumb, three search terms is probably enough. Including common words with little meaning (the, of, a, an, etc.) can waste your time. Most computer programs ignore those words because they occur in nearly every document.
Make use of 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.
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. Too many students reject articles just on the basis of the title. If the title of the article is not the title of the student's own paper/project, it is often passed over. 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 be reading 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.