Making a list of three things you are going to do in an article, or part of a chapter, is very helpful. You can tell the reader very explicitly what these three or four things are, and then go on to accomplish these tasks. What I like to do sometimes is do it first with signposting, then rewrite the list without the signposting, making smoother transitions. It's like the scaffolding of a building. You need it during the building of the building, but once the building is complete, you can take it down already.
To make the list work as an organizing principle, the items have to be parallel to one another. Like: "H.D.'s treatment of Norse, Irish, and Egyptian mythology." That's parallel. It doesn't work as well to say "H.D."s analysis by Freud, her prosody, the critical reception of her works." Then the list doesn't really organize the material at all.
One thing that is very irritating is when a writer announces s/he will three things s/he is going to say, and you cannot really tell what those three things are. The first one is obvious, but then the reader loses track, not knowing exactly when two gives way to three or three to four.