Your search strategy is an iterative process so you may need to tweak it further depending on how many results you get. Please see the Search tips on how to do this.
As you start looking through your results you may also see other keywords which you haven't thought about. Simply go back to your search strategy and add them in the appropriate place.
If you have a very limited set of results you will need to broaden the search. Ways to do this are:
Search for even more synonyms or related terms - try looking at relevant articles to identify further terms or the thesaurus or subject index.
Search on a broader topic rather a specific term, e.g. insects instead of spiders
Use truncation to increase the number of results, educat* to find education, educational, educating etc.
If you have too many to trawl through, try the below:
Combine even more keywords (add keywords for an additional concept) to make your search more specific
Limit by date range - perhaps the last 10 years?
Narrow some of your search terms to specific search fields, e.g. title only
Limit to English language only
Limit by type of material, e.g. peer-reviewed only
Use proximity searching to focus and increase relevance