1. Pronoun errors
2. Misplaced modifiers
3. Subject-verb agreement.
4. Verb Tense
But I also needed to look out for the following
A) Active voice is preferred over passive voice
B) A concise sentence is preferred over a wordy sentence
C) The orginal meaning is not altered
The best material to prepare for sentence correction is the Manhattan Sentence Correction Guide. I would highly recommend it. It helped me identify faulty parallelisms.
Sentence Correction Strategy
1) I came up with a strategy to handle the sentence correction questions. The first time I read the sentence, I make sure I understand the meaning of the sentence. My secondary objective is to see if there are any glaringly obvious mistake. I need to make sure that I understand the original meaning of the sentence so that I do not pick up a sentence that is grammatically correct but it has lost the original meaning. This happens to me sometimes because I am so lost in making sure that the sentence is grammatically correct that I have lost sight of the original meaning. Sometimes the original sentence is so messed up that it is hard to follow. A quick scan of the answers choices will help you get the original meaning. At this time, you can eliminate any answer choices that have altered the original meaning as they are always wrong.
2) The next thing I do is apply the grammar check given above. I initially use 1 through 6. After applying the initial grammar check, I am usually down to 2 choices.
3) I then apply check 7. If both sentence pass check 7, I then chose one that is concise and uses an active voice.
Sentence Correction Idioms
To apply check 7, you need to know the frequently used idioms on GMAT. Here is a list of idioms I found on the web.
I hope you guys find this list useful.