Keyword searching is the type of searching you typically do in PubMed, CINAHL, MGH OneSearch, and many other databases. At it's most basic, it looks at the words you type into the search box and finds articles that contain those words in their titles and abstracts.
Finding the Right Keywords
Because you are looking for words that appear in titles and abstracts, it follows that you need to know which words authors are using to talk about your topic. This can present some problems when you are at the beginning of a project, because you may not know much about your topic and the way people are talking about it yet. That's why your first few searches are less about finding the perfect articles and more about reading titles and abstracts so that you can find the right keywords.
As you read through the titles and abstracts, start collecting words you think might be good search terms.
Organizing your Keywords
Your topic will most likely be made up of several ideas. You might have some words that describe the population you're investigating. You might have others that describe outcomes you are looking for, and so on.
As you collect words for searching, it can be helpful to group these words by idea to help keep yourself organized. Making lists can also help you brainstorm synonyms and alternative endings as well as help you identify areas you're not so sure about.
For example, if I wanted to find information about whether exercise was effective at decreasing fatigue in women who have breast cancer, I might start a chart like this one.
Most databases and search engines use Boolean operators to connect your keywords. The operators not only let you combine the different ideas of your topic but also include the synonyms and word variants.
The two most common operators are AND and OR. AND combines different ideas so that you can find articles that contain both terms. OR combines similar ideas so that you can find articles that contain either/any of the terms.
If we use our example topic about women with breast cancer, we might use the connectors like this:
(fatigue OR energy OR tiredness) AND (exercise OR exercising OR yoga)
NOTICE that I put the terms connected with OR inside parentheses. You'll need to do this if you want your search to be interpreted correctly by the search engine.