The usual structure of a paper follows this pattern: the introduction paragraph, body (supporting) paragraphs and conclusion. In the introduction you introduce your argument and the issue you are going to be discussing in the paper. The intro paragraph ends with your thesis statement - which states what exactly you are trying to argue about this issue and perhaps propose a solution. The body paragraphs usually provide support for your argument where you can use secondary sources and other information to back up your opinion and make you sound credible. The conclusion paragraph sums up your argument and sometimes offers a resolution.
I try to use what I have named the AEC Method. This sets up paragraphs as so:
Assertion: Make a point or argument. This sentence is often shorter and more emphatic because it is opinion.
Evidence: These are either quotes, paraphrases or numbers that can be used to substantiate your point. This evidence is very important so that you can defend your argument with raw facts.
Commentary: Here you explain why the evidence supports your point. Now, I don't want to give the appearance that this MUST be one sentence. Often times, both the evidence portion and the commentary portion can become a bit more complicated.
Also, don't worry to much about keeping the exact order, though I would recommend that. One of the best features of this model is it keeps your writing organized. Keeping the model in the order presented can work just as well as changing it up, so don't feel it is necessary.