There are several short tutorials and help sheets created at Colorado State University that address Boolean Logic and other helpful steps when searching databases:

Truncation and proximity operators can be helpful to narrow or broaden a search in an electronic database. 

Truncation is a mechanism for searching multiple terms that begin with a desired prefix. For example, "build" with a truncation symbol will search for build, building, buildings, builder, etc. The symbol varies from database to database. The truncations symbol is frequently an asterisk (*), dollar sign ($), or plus sign (+). In some databases, truncation is used to search for the root word only. Read the help screens in the database for exact details.

Proximity operators are a way to ensure that search terms appear next to one another, within a certain number of words, or appear in the same sentence, paragraph, or field (part of a record; for example, title or abstract). "With" and "near" may have different meanings, depending on the database, so always read the help screens for details. 

Please note: Not every database supports truncation and proximity operators.  Check the help screens for each to find out if these useful operators are supported. 

When searching databases, most searchers use "boolean logic" to create searches that try to incorporate as many different ways of describing a subject or concept into one search. 

Using connectors in your Boolean search queries. Borrowed from the Information Resource Centre Blog.

This video describes (in easy to understand language) the concept of boolean logic and how it is used in constructing good searches. 

Boolean logic was invented by a British mathematician named George Boole. Here is a link to a short biography if you are interested in learning more about him: George Boole (WSU Access ID & Password Required)

This second video uses boolean logic to make a peanut butter and jelly sandwich!