An argumentative or persuasive piece of writing must begin with a debatable thesis or claim. In other words, the thesis must be something that people could reasonably have differing opinions on. If your thesis is something that is generally agreed upon or accepted as fact then there is no reason to try to persuade people.
There are three types of rhetorical appeals, or persuasive strategies, used in arguments to support claims and respond to opposing arguments. A good argument will generally use a combination of all three appeals to make its case.