Write down the question that you want your paper to answer.
What are some sustainable energy technologies for rural communities?
Next, underline the nouns and important adjectives in your question.
What are some sustainable energy technologies for rural communities?
Looking only at the underlined words, use your formatting tricks to optimize your search.
Chunk them together with an AND, then do your search!
sustainab* AND energy AND "rural communities"
To get better results, do the basic stuff above but also try to think of synonyms and related concepts for your underlined words. Get creative!
Once you have your list of synonyms, link them together with OR and stick them all inside a set of parentheses.
Combine that back with your other search terms, use your formatting tricks, and you'll have a really powerful query.
Don't limit yourself! Look for synonyms and other related concepts that can be useful. Instead of sustainable energy as a general concept, try thinking up more specific concepts that work:
Once your search is pulling up good results, click through on some of the article titles to see all of the information used to describe those articles--the metadata. Look for the subject terms or author-supplied keywords used to describe the articles that are best for your needs, then incorporate those terms into your search strategy.