To produce a sustained argument (rather than a chaotic jumble or a reductive five-paragraph essay), always use functional topic sentences and PIE.
Functional topic sentences
1. Tell the point of the
paragraph and
2. Tell what that point
has to do with the thesis
That is, every paragraph should bring in or refer back to the larger argument (thesis) as it makes the point particular to that paragraph. That way your thesis develops and becomes more complex as you go rather, which is the mark of a sustained argument.
Make sure that everything you discuss in the paragraph falls under the umbrella of the topic of the paragraph. You may also find it helpful to end each paragraph with a sentence that summarizes the point you've made, especially if the paragraph is long or the argument complex.
When you finish drafting your paper, string together all the topic sentences; they should summarize your argument. If they don't, fix the essay by moving paragraphs around, dividing up topics, or adding paragraphs where argumentative points are missing.
You can use the strung-together topic sentences
as a basis for your opening paragraph or thesis statement, if you're having
trouble writing that. This is also a way to assemble the points you'll
want to cover in your conclusion.
PIE is a method for effectively incorporating outside sources into your essay.