I think that much of this is going to depend on if you have a specific method or guideline that has to be followed. If so, this will probably play a large role in organization of the essay. The opening paragraph could serve as an introduction, where you discuss the general influence of Coca- Cola advertisements and discuss the effectiveness of such advertisements and how they occupy a particular importance in product consumption. If there is a particular thesis statement about the analysis of the advertisements that is needed, the end of this introduction might be a good place to insert this important and needed element. Then, I think you would probably want to spend a paragraph or so on each advertisement. In each paragraph, you can probably discuss the specific advertisement, elements of persuasive advertising in it, and other techniques of persuasion, as well as how the specific advertisement helps to support your thesis statement. The conclusion might be a more specific restating of the thesis statement and explanation as to how there could be some shared commonality regarding persuasive techniques in Coca- Cola advertisements. This is a fairly direct approach to organizing expository essays and it might an effective one to pursue here.