For example you may need to know how to use the 'map term to subject heading' option in Medline, or how to do chemical structure searching in Scifinder Scholar. Use the and operator to narrow your search. Use the or operator to broaden your search. Truncating your keywords will broaden your search. Use truncation to retrieve variations of your search word.
Different databases use different trucation symbols.
Most databases use descriptors or subject headings which are specific words or terms which are used in the database to describe a topic. You can carry out a more systematic searching by taking note of relevant descriptors and subject headings.