The right search terms are the most important conditions for an effective search.
General tips:
- Think 'in terms of' the article to be found. What words are likely to be used in the article you hope to find?
- As a result of your findings, correct your search terms a few times in the initial phase of your search
Keep in mind the different kinds of terms:
- synonyms
- broader terms
- narrower terms
- related terms
- antonyms
- translation into languages relevant for subject and discipline
- Think, for each of these categories, of the different forms (single, plural etc.) spelling variations and possible abbreviations/acronyms)
You don't have to think of terms all by yourself. Use the tools:
- words from an introductory article in Wikipedia for instance
- words from search result pages in search engines
- keywords from previously found sources (especially the so-called 'author keywords')
- dictionaries, for translations and for looking up the meaning of words
- thesauruses, for finding related terms that you may not have thought of
