Try to answer the questions posted in the forum with explanations. Make flash cards and practice a lot. Its more important to review as well. While reviewing SC problems try to identify all the errors in a wrong option don't stop with one error.

Check out these posts for Ron's take on how to work on SC.

https://www.beatthegmat.com/how-to-impro ... 88594.html
https://www.beatthegmat.com/how-to-prepa ... tml#403863

The advice sam2304 gives is excellent. At the risk of pointing out the obvious, the OG is still the best source of explanations for what GMAC wants out of SC, and thus should be at the core of any study plan. It doesn't explain the actual grammar rules as well (which is where your Manhattan books will come in handy), but it does explain how GMAC prioritizes and values different rules of grammar and (in particular) style.

All of this advice is right on. I'd focus on the Most-Tested SC concepts first, so you don't get overwhelmed. Here's what to look for first:

1. Pronoun-Antecedent Agreement - The most common error associated with pronouns is pronoun-antecedent agreement. The antecedent is the word the pronoun is replacing. A pronoun must have a clear antecedent in the sentence; the lack of an antecedent is itself an error. The antecedent may often be present, but will disagree with the pronoun in number.

2. Parallelism - Parallelism is tested on the GMAT in a series of phrases or items in a list. In parallel construction, the phrases or items must be in the same form. This can be tested with a number of parts of speech: nouns, verbs, prepositions, etc.

3. Modification - Modifiers are words and phrases that describe nouns. Adjectives, adverbs and modifying clauses will be incorrectly placed, or in the wrong form. Adverbs can only modify verbs, while adjectives modify nouns. Be on the lookout for suspicious adverb-noun and adjective-verb pairings. Also be aware that many sentences will begin with a modifying phrase and a comma. The subject after the comma must be the person or thing doing the action of the modifying phrase.

4. Comma Splices - A comma splice, also called a run-on, occurs when two sentences have been improperly joined with a comma. The most concise way to fix a comma splice is to change the comma to a semicolon. If you see a semicolon on a Sentence Correction, check to make sure there's an independent clause on each side.

5. Sentence Fragments - The fragment is a dependent clause. It is missing a subject and predicate verb. To fix the fragment, we would need to add an independent clause or the missing information.

6. Idioms - Idioms are expressions native to the English language. There are two part Idioms such as "neither...nor" and" between...and" as well as prepositional idioms like "interested IN" and "afraid OF."

7. Subject-Verb Agreement - SCs love to give long sentences where the main subject and the verb are separated by many words or clauses. You must identify the subject of each sentence and make sure the verb matches it in number. Generally, a plural noun takes a singular verb and a singular subject takes a plural verb.

8. Active Voice v. Passive Voice. The GMAT generally prefers active voice. Try to place the subject at the front of the sentence, followed by its verb, followed by the object. Sentences that place the object first and/or use the word "being" are typically incorrect.

9. Diction - Words like "who", "that", and "which" have their own special rules. "Who" can only refer to people. "That" introduces a relative clause and is used to replace things. "Which" introduces non-essential information.

10. Clarity/Meaning - On the GMAT, you have to take the overall meaning of the sentence into consideration. This is especially going to be tested more in 2012 since the GMAT is gradually moving away from Idioms. The correct choice will be grammatically correct, but will also be clear. If you narrow it down to two choices, look for subtle differences in meaning.

Thank you all for taking time to reply.

There is no easy way round for a native speaker. Read Manhattan SC to the point you can remember the subtopics of each chapter and explain it to someone. This will require reading Manhattan SC a number of times. Make notes for points examples that you find are not intuitive to you. Take each example in Manhattan SC as a GMAT question and see if you it appears obviuos too. If not then take notes of that example. Revise,Revise, Revise.