Concepts - Databases generally want keywords (synonyms & controlled vocabulary) rather than an entire question.
For example: rather than typing "Which is better for acute coronary syndrome: drug-eluting stents or bare-metal stents?" just pick out the key ideas:
acute coronary syndrome
Then look for synonyms, variant spellings and controlled vocabulary as described below.
Synonyms - searching for synonyms will broaden your search, for example: cancer OR neoplasms OR carcinomas
Variant Spellings - American and British spellings are oftentimes different, so searching pediatric OR paediatric gives broader coverage.
Databases and Controlled Vocabulary (Subject Headings)
PubMed and Medline - MeSH
CINAHL- CINAHL Headings
Cochrane Library - MeSH
Embase - Emtree
Scopus & Web of Science - None
Abbreviations - If the abbreviation is well-known you may want to search both the abbreviation and the full name (i.e., AIDS OR Acquired Immunodeficiency Syndrome); other abbreviations may bring up too many false results
Quoted Phrases - The use of quotation marks around a phrase such as "end of life" or "stress reduction" assures the words are found together and cuts down on unrelated citations. Don't use quoted phrases that are identified as controlled vocabulary terms.
Truncation - use of a symbol to search the stem of a word with any ending. For example, test* would include tests, testing, tested. Most databases use the asterisk (*) as the truncation symbol. Don't use truncation on terms that are identified as controlled vocabulary as it turns off the mapping that is happening in the background.
Field Searching - this allows you to search for terms or phrases only in the title and abstract, or just as a text word. How you do this varies in each database. In PubMed, to search title and abstract you add [tiab] after your term.
Parentheses - The parentheses are important in searching, just like in math! When constructing you search, keep your "OR" phrases as distinct groups. One way to do this is to create a parentheses pair for each set of synonyms you will be searching joined by AND. So you would start with something like this: () AND () AND () for three concepts. Parentheses ensure that the database doesn't apply the wrong Boolean operator to the term. Now go back and put in your OR phrases: (saw palmetto OR serenoa repens) AND (benign prostatic hyperplasia OR prostate hypertrophy OR BPH) AND ("disease management" OR "illness management").
An easier way to do this may be to construct your search by searching each concept separately and then joining them together using your search history or Advanced Search. There may be times when a controlled vocabulary term bridges two or more concepts that will need to be OR'd into the search. The important thing is to keep the concepts separate or you'll end up with many irrelevant search results!
Adjacency - some databases allow the use of symbols to show nearness or adjacency between words such as N3 or W3. Check the help files to determine if the database you are searching allows this. Ovid Medline, Embase and CINAHL all allow some form of adjacency searching.
For best results, use a combination of all the search tips!