Farooq,

I am also continuously working on my verbal part. I am not a master of the subject, and here is my 2 cent.

Personally, I feel that building command over English takes time. It might take 6 month, 1 year, 3 years or more, depending on from where we start the race. Considering you already have enough of information and material to work on your verbal section as whole, let’s see SC in particular. Following is my strategy to tackle SC:
1.Read the full sentence first. Don’t start finding faults even before understanding the sentence.
2.Read the sentence from start to end, don’t skip any word or start finding fault while first time reading the sentence.
3.Read non-underlined part (NUP) of the sentence very carefully because your underlined part (UP) can change but NUP can’t.
4.Correctness of UP depends on NUP.
5.Point 1 to 4 are the most important points.
6.If some SC question and its options are very lengthy then read only once. Click the option that you found the best after first read. There is no point in repeated reading of the question or the option. Don’t waste time on such questions.
7.Look for signals.
8.Finish each question in 1 to 1.5 mins

Important points:
1.Understand the complete sentence.
2.Look for signals
3.Apply grammar rules
4.Understand the GMAT style, which might be different from our day-to-day English that we read and speak.

Material: Manhattan Sentence Correction is worth going through. You even get the soft copy of old version of the book on the net.