I find that the best way to approach these problems (and I'm just starting off!) is by doing the following:

1) Read the question stem and get a feel for what is going on.
2) Here is the one best step I have always followed after reading the preview of MGMAT's SC, and my scores have improved dramatically in SC:

Do NOT plug everything back in and see if it works. Instead, focus on the differences between the answer choices and see which ones are wrong. Throw away the wrong ones and keep the right ones.

After doing this, my sentence correction scores went from 7/15 on my first GMAT to around 12/15. This is after preparation for less than a week, so clearly, this is working!

sykw08,

You got good tips from Domnu.Apart from that, you'll generally get SC questions in the pattern 2:3.

For e.g.
The government requires that these forms should be submitted before the end of the financial year.

A. that these forms should be submitted
B. that these forms be submitted
C. for these forms to be submitted
D. these forms submission
E. these forms should be submitted

Choice A and B clearly follows the idiom - "requires that" and hence you don't even bother analyzing choice C,D and E.

Although there will be some exceptions in this 2:3 pattern, you will generally get such questions in the SC.

Give yourself sometime, analyze ur weakness and that's it ..you are a pro in SC:)