Since I'm a native speaker, the sentence correction wasn't too tough for me, but I did have a lot of improvement in it.
Obviously, the best thing is to try and spot the error right off the bat. If you can do this, then you can either find the answer or you're probably down to two choices.
If you can't find the error, then read all the sentences in comparison to the original. Pick out the differences and figure out which one is right. Once you spot the difference, you can probably find the same mistake in the other choices, so you can cross those out as well. Then if some still remain, you'll just have to go with what sounds right (I know this will be hard).
Two last tips:
1) When in doubt pick the shorter one
2) In my experience, it seems like choice A is right more often than you would think, so if you haven't picked choice A in 4 or 5 SCs and you have to make a guess, A might be a good guess if it's still remaining after POE.
"Egotism is the anesthetic that dulls the pain of stupidity." - Frank Leahy