trouble figuring out the right rule

Follow the steps to solve Sentence Correction:

STEP 1: Read the full sentence & understand meaning.
STEP 2: Scan & Eliminate on bases of rules/idioms - Subject Verb Agreement - Parallelism - and others
STEP 3: After filtration, take care of meaning clarity [M]
STEP 4: If you are still left with answer choices, look for preferences Exceptions

Preference --> whether > if , rather than > instead of, etc
Exceptions --> Subjunctive Sentences


Also, next time you do the Topic-wise question, don't just check for the errors related to that topic but look for Subject, Verb, Parallelism and MOST Important.. MEANING.

This method helps me!

Probably the biggest mistake that test-takers make on Sentence Correction is that they don't prioritize error types - they see a wording difference between a couple answer choices and they latch on to that and try to find/remember a rule.

What you should do: Know what you're good at and make those decisions first. Look specifically for opportunities to do what you do well. And you should get good at - and then look for:

Modifiers
Verbs (both subject-verb agreement and tense)
Pronouns

and then Comparisons/Parallelism.

The "MVP" errors come up the most frequently, and if you're looking for them they're usually the easiest decisions to make. But where I see students get lost over and over is that the Pronoun decision, for example, is in the middle or toward the end of the answer choice whereas the first few words of the answer choice are a different decision, and a decision that very few of us do well.

For example, one of my favorite OG problems has always been:

The Emperor Augustus, it appears, commissioned an idealized sculptured portrait, the features of which are so unrealistic as to constitute what one scholar calls an “artificial face.”

(A) so unrealistic as to constitute
(B) so unrealistic they constituted
(C) so unrealistic that they have constituted
(D) unrealistic enough so that they constitute
(E) unrealistic enough so as to constitute

Most students try to make the "so unrealistic as to" vs. "so unrealistic that" decision first...completely ignoring the verb tenses at the end of the sentence. But you should be looking for verb tenses first - C is the most popular answer among those who read from left to right and make their decisions that way, but for those of us who scan for "MVP" decisions, we'll realize quickly that the past-tense "constituted" is wrong (the features ARE - present tense - so unrealistic as to CONSTITUTE, also present tense). So the answer is A, but most people eliminate A because they know the idiom "so X that Y" and they don't know the idiom "so X as to Y", which is absolutely correct...just less common.

So...to more succinctly answer your question - the best way to make SC decisions isn't necessarily to look for "the right rule" but rather to seek out "the rules I know I do very well". For most of us, that means looking first for Modifiers, Verbs, Pronouns, and Parallelism.