Hey Ashetty,

Glad you brought this up! Perhaps one of the bigger challenges out there with studying grammatical rules for GMAT SC is taking those rules and applying them - having the ability to use them and not just "know them". So I wouldn't suggest "going through the SC book again". The challenge is taking those fundamentals and applying them to thought processes and techniques - make the strategies and rules work for you.

So for example, you mention verbs as a challenge. You can know the verb tenses backward and forward (present, past, past perfect, present progressive, subjunctive, etc.) but you don't get points for knowing those terms. You get points for being able to determine when a verb tense doesn't make sense. For example:

As I was writing this post I will check for grammar and punctuation.

That's wrong, because the phrase "as I was writing" is in the past and the phrase "I will" is in the future. That's an illogical timeline - it just doesn't work. Similarly:

As I was writing this post, I had checked for grammar and punctuation.

Again, this is illogical. "As I was writing" sets up the timeline that those two things (writing and checking) happened at the same time, so it's illogical to set one before the other - I've already said "the same time".

Now, where I think many "grammar studiers" struggle with this stuff is that there isn't one required way to phrase this sentence. You could really use any verb tenses that make sense together - verbs that provide a logical timeline:

As I was writing this post, I checked for grammar and punctuation. ---> Correct. Both events rightfully happen in the past even though they're technically different tenses. The important thing is that the timeline makes sense. During the course of writing, which happened in the past, I checked (also in the past) for grammar and punctuation.

As I was writing this post, I was simultaneously checking for grammar and punctuation --->Also correct. Here I use the same tense but what's most important is that the timeline keeps both events in the past because of that "as I was" setup...we need these things in the same time.

My point? The most-overlooked (but I'd argue most important) component of GMAT Sentence Correction is that logical element, that ability to look at the verb tenses, modifiers, whatever and say "that doesn't make sense". Because, think about it, b-schools aren't looking for copy editors, they're looking for critical thinkers. They want people who know enough to say "that's just not right". Knowing the functions of verb tenses can be helpful for this, but more important is your ability to apply that knowledge to assess whether or not you have a logical timeline.

So my suggestion - at this point don't "study"..."think"!