Unfortunately sentence correction requires you to know most of the rules to get correct answers becuase there are no rules that are considered easier or harder and many questions contain multiple rule errors. However, by focusing on six of the main errors you can get the most for your studying.
Those six are Pronoun, Parallelism, Subject/verb, Misplaced modifier, Idiom and Verb tense. If I had to eliminate one it woudl be idiom simply becuase those need to be memorized most of the time.
The rules are actually not that hard to study on their own, it is how you study them that is important. Learning the key words that indicate a certain error is being used and then knowing what parts of the sentence to separate out to determine the correct answer is key to doing your best on sentence correction.