This search advice varies in where it is located and what it is called. Some SE's give the user a great deal of freedom and flexibility in structuring Web searches while others are more rigid. That is, they automatically retrieve any word that can be built on a common stem. You need to know if you can turn this feature on and off. SE's handle phrases in several different ways.
Case sensitivity can be useful when searching for names.
These can be little words, such as articles and prepositions. Some SE's will not search on numbers, single characters, or symbols. Searches such as Interferon Beta, Interleukin 2, CT scanning, and quality of life can be problematic. Check to see if your SE has a list of its stop words to be sure it is searching what you enter. Realize that SE's do not understand concepts.