You may list more concepts and more possible terms/concept initially than you actually need for the search. Go ahead and gather as many as you can in your initial brainstorming. Decide later which ones you you want to use.
Limits can be AND'ed in as concepts (English[la], clinical trial[pt], 2005:2011[dp], adult[mh]) or selected from the Limits page
About 'Text' fields:
Don't forget to look at the MeSH terms on relevant articles to find new terms; also look at titles and abstracts for new terms. Add them to your list. Try different combinations.
Remember: It is extremely rare that only one attempt a search strategy is enough. Try multiple search strategies.
The Practice Question is:
How effective is the prophylactic use of ondansetron for preventing postoperative nausea and vomiting in adult surgical patients?
1. Parse the question into concepts
2. List terms for each concept including both textwords and MeSH subject headings
3. Use terms to create search strategies and run them in PubMed
4. Look at results
a. How many abstracts did you get?
b. How can you increase the yield?
c. How can you decrease the yield?
d. How relevant are your results
Precision = the fraction of retrieved items that are relevant
(How much of what you retrieved is good?)
# relevant articles
# total articles
Recall = fraction of relevant items retrieved out of all relevant items available in the database
(How much of the good stuff did you actually get. Unfortunately, the higher the recall, the more 'junk' you end up getting also.)
# relevant articles retrieved
# of total relevant articles available
When searching, you're looking for a reasonable balance between precision (narrowing your search to get ONLY relevant articles) and recall (widening it to get ALL relevant articles, which usually means a lot more junk to weed through as well).
A common question is "How many articles should be retrieved by a good search?" There's no exact answer to that. Somewhere between 100-300 is a reasonable number of abstracts to weed through, but it depends greatly on your question, how comprehensive you want to be, and how much literature there truly is on your topic.