1. Use OR to combine similar terms; group similar terms together
2. Use AND to combine your main concepts.
Databases search for an EXACT match, so you'll want to think about variations of a word-ethic, ethics, ethical. Fortunately, many databases have a built-in shortcut that will signal to the database to do this for you--the asterisk.
SO, instead of searching for: ethic OR ethics OR ethical, we can just search for ethic* --this finds every word that begins with e-t-h-i-c
Symbols sometimes vary from database to database. Look in the database Help for "truncation symbol".