The ACT English section tests both reading and writing skills simultaneously, and it is necessary to change your approach based on the type of question you are being asked. While grammar questions require you to recall specific rules, rhetoric questions require you to apply specific concepts about how paragraphs and essays work: what makes an effective transition (what is the logical relationship between two ideas?); how a paragraph is most logically developed; and what constitutes relevant vs. irrelevant information.
Unlike grammar questions, rhetoric questions can be absolutely, perfectly grammatically correct yet still be wrong. You can’t be fooled by how they sound — you actually have to think (yes, think!) about whether they go along with the main idea of the passage or paragraph in question.
In short, they’re reading questions, not writing questions. And because this is the case, you have to treat them like reading questions.
That means going back to the passage, figuring out the gist of the section you’re being asked to deal with, and figuring out what sort of information would be relevant.
One of the biggest mistakes I consistently see people make on rhetoric questions is to start by looking at the answers and assuming they’ll remember the content well enough to sort everything out rather than going back to the passage and working out the answer for themselves beforehand.
When most people read the passages as they’re working through the questions, though, they’re usually only really paying attention to grammar rather than content. They’re not thinking about main ideas and supporting information but rather about whether that comma in #27 was really supposed to be there. So when they’re asked to insert/delete information, they don’t really have the full context for it.
Remember: the readings on the English section are pretty simple. It’s usually not too hard to figure out their main idea and thus whether a particular sentence or part of a sentence should be used to support it. Yes, it may take a whole 30 seconds, but that’s time better spent actually figuring out the answer than staring at two options and trying to decide between them. So to sum up:
1) Read the question and identify exactly what you’re being asked to insert or delete.
2) Go back to the passage and read as much as you need to figure out the main idea of the passage or paragraph. For questions that ask about the passage as a whole, check the title: it’s there to tell you what the passage is about. For questions that ask you about the middle of a paragraph, read the topic sentence. Conversely, if you’re asked to insert the first sentence of a paragraph, jump ahead and read the middle of the paragraph.
3) Ask yourself whether the information in question is relevant to that topic and why/why not.
4) Look at the answers. The right one should pretty much pop out at you.