When you have selected the database you are to search in, there is most often a simple search box or an advanced one with more possibilities for limiting. In each database help is available to see how the search language works, so it’s a good idea to check there before you start searching since the search routes vary depending on which search service you choose.
When I find too much?
If you for example start with a search word/keyword, you can add a further one to get fewer hits. If you want to match the result so that all the words are there, you formulate it either with a space or with an AND between the search words.
Example: teachers AND schools.
Then both terms have to be among the hits, and you limit your search with each new search word.
When I find too little?
If you combine the search words/keywords with OR you will expand your search and get more hits. Then either the one or the other word, or both, will appear. It may be of use if you search for synonyms or forms of a word.
firms OR enterprises OR corporations OR companies
Another way of expanding your search is to search for the word stem and insert a truncation symbol, most commonly an asterisk. Then you will get all the endings of the search word. For example, school* will give hits for schools, schooldays, schoolboys/-girls et cetera.
Sometimes you may perhaps want to search for a whole phrase, so then you insert quotation marks to match the result so that the words come together in a sequence.