Let's say our research question is this: "What role does mindfulness practice play in the lives of college students?" Here are some tips and tricks to help us craft effective keywords and enact a good search strategy:

Use Boolean Operators
Including "AND" and "OR" in your search can help you find more precise results.
Example search term: mindfulness AND college students

Don't forget quotes
Put phrases in quotes so the database will search that collection of words as a phrase rather than as single words. 
Example search term: mindfulness AND "college students"

Use synonyms
Are there any other ways we can phrase the terms in our search? Using synonyms with an "OR" helps broaden our results.
Example search term: mindfulness AND ("college students" OR "university students" OR undergraduates)

Use truncators and wildcards
A truncator (most commonly an asterisk, but it varies across databases) helps extend your search to include various word endings while a wildcard (most commonly a question mark) substitutes a symbol for one letter of a word.
Example search term with truncator: mindfulness AND child* - (finds results with child, childs, children, children's, and childhood)
Example search term with wildcard:  mindfulness AND wom?n - (finds results with women and woman)

Pay attention to your results
When doing a search on anything, think of the results as you get back a glimpse into the landscape across a particular subject. They might not be the right results for your particular question, but taking the time to "read" those results can tell you something about your research topic that may be helpful.
For example: A search on mindfulness and college students returns a lot of results - some having to do with mindfulness practice alleviating depression and anxiety and enhancing well being, and some having to do with mindfulness practice aiding in improved academic performance. This may cause us to think -- do we want to refine our search to one of these tracks of thought?