Boil your topic down to the most important words. Ignore superfluous words like in, the, of, with, against, affect, impact. Begin with a keyword search.
Put each "different piece" of your topic in a separate search box. Using the topic of "histological study of Artemia blood cells in immature animals" as an example below, note how each different piece of the topic is entered on a separate line. Leave the AND off to the left as it is. Synonyms for the pieces are connected by OR--and kept on the same line--as seen below...
Too many results? Focus your search by searching for your keywords in the ABSTRACT field or the TITLE field. Or...narrow your search a bit by searching a particular species of Artemia.
Too few results? Think of synonyms. Add synonyms to your search--using OR--and keep your synonyms all on the same line. Artemia or brine shrimp. Hemocytes or haemocytes or haematocyte or hematocyte.
Increase your results by removing the least important "piece" of your search while still retaining the "essence" of your search--in the example above, perhaps you could remove the immature piece.
Still no results? Broaden your search slightly. Still no luck? Try searching a different journal article database.
When reviewing your results, look for relevant "subject" or "descriptor" words. Find subject terms either on the results page, or at the end of individual records. Write down relevant subject terms that you find.
Go back to the search screen and using the subject terms you discovered, search your subject terms in the subject or descriptor field. Subject terms are gold threads--they will almost always lead you to the most relevant results.
No PDF icon? Use the link to find full-text.
No full-text? Use the Interlibrary Loan link to request a copy of the article or book from another library.
Be sure to take advantage of boolean operators, exact phrase searching, and field searches.