The Craft of Research: intro to part 3; chapter 7

Part 3 deals with the relationships between drafting (the first draft! which they recommend you do only when you have a pile of information, sufficiently sorted), arguments, and conversations. That sorting of data, however, is weakest in a linear order, one with only "a plausible sequence." You must have a stronger organizational plan in mind - "not from the categories of your data but from your own questions and their answers." That organizing principle will be your central claim, a.k.a. argument, a.k.a. conversation with readers.

So how to make a good argument? That's what chapter 7 is about, a survey of the parts of argument. Here they are; the first two must always be stated plainly; the third, often.

• Claim: what you are asking your readers to believe.
  
• Evidence: data or logic that backs up your claim.
  
• Warrant: answers "How is the evidence relevant to the claim?"
• Qualifications: limiting, accuracy-increasing factors to the claim. This isn't waffling.

An example of all four parts (emphasis in orig.):

Your [blood sugar] reading is 200 {evidence}, so you should be checked {claim}, because that much glucose in the blood is a good {qualification} sign that you may {qualification} have diabetes {warrant}, unless, of course, you just ate something sugary {qualification}.

As your argument becomes more complicated (and therefore interesting!), you'll need more of the above types of qualification.