Start with one word or concept and add additional concepts as necessary.
Many abbreviations or acronyms that are common in daily work and patient care may be unrecognized by databases. Acronyms can stand for more than one thing, causing a search to bring back results on a completely different topic.
Generally, using quotation marks keeps exact phrases together, for example "occupational therapy". Exercise caution here. A database, like PubMed, may not recognize the quoted phrase — especially when used in combination with a field command.