Too many results means you'll want to try to...
Try ANDing a different search term into your search to narrow down the results. Or try NOTing a search term: if you don't want to look at results from a particular country, NOT that country out. Confused by the AND and the NOT? Check this out.
Limit your results with limiters. Sometimes they'll be found off to the left after you run your search, or ...underneath the advanced features. Not seeing them? Look around, they're there! You can usually limit by language, publication type, publication year, peer-reviewed....normally you'll be provided with a number of ways to focus/limit your search.
You can search for your keywords in a particular field. Information records are organized by fields--some examples fields: author, title, journal title, abstract. To field search, choose the pull-down box next to your search term box. Select the field you'd like to search within. Fields that are helpful to search within: title, abstract, subject. A title is a pretty tight search, that type of search will whittle down a large number of results quite quickly. An abstract field search is a bit looser. Subject's a good field to search in, but you'll first need to "find" the correct subject term in order to use it. Remember that you can't "make up" subject terms; you have to find them first to use them.
Realize that field searching--particularly abstract and title--is a double-edged sword. Use those fields cautiously. If you have 10,000 results, it can be useful, it will cut through them very quickly and make relevant results pop up.
It is bad in that it will get rid of good results that may have been about your topic, but which did not include your keywords in the title or abstract. It is not wise to use a title search for something that is extremely important to you.
Sometimes just choosing the right sort will cause the articles you want to rise to the top of the list, or will group like things together. Common options include:
Too few results means you'll need to consider trying...
As long as you find one good scholarly article or book, you can look up the works cited in the footnotes or bibliography to find the sources it's based upon. Generally the sources in the bibliography will be relevant to your topic--it is to your benefit to use them. The only problem with this is that works in the bibliography will be "older" than the article in hand.
You can also follow citations in the future, that is, those works that have cited your article AFTER it's been published by looking up who cited the work you have. Google Scholar is excellent for this. Paste your article title into Google Scholar; and click on the cited by link underneath the article title.