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
• drug-eluting stent
• bare-metal stent

Then look for synonyms, variant spellings and controlled vocabulary as described below.

Synonyms

Use synonyms to broaden your search and ensure that you are not missing out on a concept. For example, if you are searching for cancer, your search might be:

cancer OR neoplasm OR carcinoma

Variant Spellings

Terms may be spelled differently depending on whether the author uses American or British spellings. For example, if you want to search for pediatric, including the British spelling of paediatric will give you broader coverage. 

pediatric OR paediatric

Abbreviations

You may want to include both the abbreviation and the full name for well-known acronyms 

 AIDS OR Acquired Immunodeficiency Syndrome

Test this carefully as some abbreviations may bring up too many false results!

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!

Some literature databases index commonly used terms to help you search for articles more effectively. Here are some commonly used databases in health sciences literature and their controlled vocabulary: 

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.

Most databases allow you to use 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.

As with other search tricks, you may need to test this as some databases may turn off mapping taking place in the background if you use truncation for controlled vocabulary terms. 

Use field searching to narrow your search to specific areas of an article, such as the article's title.

To do this in most databases, look for Advanced Searching and investigate the drop-down menu to select the field you want to search. Many databases offer a shortcut you can add into your search. For example, in PubMed if you want to search for a term in the title and abstract fields, you add [tiab] after the term such as:

asthma[tiab]

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.