To '''assume good faith''' is a fundamental principle on any wiki, including Wikipedia. As we allow anyone to edit, it follows that we assume that most people who work on the project are trying to help it, not hurt it. If this weren't true, a project like Wikipedia would be doomed from the beginning.
So, when you can reasonably assume that something is a well-intentioned error, correct it without just reverting it or labeling it as vandalism. When you disagree with someone, remember that they probably believe that they are helping the project. Consider using [[Wikipedia:talk page|talk page]]s to explain yourself, and give others the opportunity to do the same. This can avoid misunderstandings and prevent problems from escalating. Especially, remember to [[Wikipedia:Don't bite the newcomers|be patient with newcomers]], who will be unfamiliar with Wikipedia's culture and rules.