Generally speaking, when you conduct a subject search in a library catalog such as MaineCat or Minerva, your results will be fewer and more focused than doing a keyword or a word search.
Generally, many databases will search two words together as a phrase. Using double quotation marks will also let you search by phrase in just about every database. EBSCOhost databases have many nifty search options under search modes. Proquest databases automatically search two words together as a phrase.
See how the use of Boolean operators affects a search in Academic Search Premier
Use a Thesaurus.
EBSCO database tutorial
ProQuest database tutorial