Excerpts from my debrief ... hope they help.
Sentence Correction:
MGMAT is the best book you can get your hands on to prepare for SC.
Aristotle Grail is a simplified version of
MGMAT and is too useful to build the concepts.
Magoosh lessons. Easy, Crisp and Lucid video lessons.
Take down the notes in your notebook and revise them every other day, so that they are embedded in your system.
Start off a SC question by find the subject and then check that the verb agrees with it or not. Check for the parallelism by looking out for words such as and, that etc.
Make sure that there is a verb in the sentence (-ing forms are not verbs by themselves)
To break it in points:
1. Find the subject
2. Make sure the subject agrees with the verb in numbers
3. Make sure the verb is full verb
4. usage of Like (used to compare nouns and express similarities), as(used to compare every thing else and such as used for examples)
5. Parallelism- Pay attention to ""and, that, either or, neither nor etc" as they are the signal words and parts on both sides of these words should be parallel
5. Tense: The parallel parts of the sentences should be in the same tense.
Perfect Tense used only when any event has already happened and is over
Progressive tense is used when the event is in action.
These are some of the things which will enable you solve most of the questions correctly.
SC: the-most-comprehensive-collection-of-everything-official-sc-140372.html#p1129819
Download the collection by Souvik and solve. Note down all the questions you get wrong and then search out on gmatclub about the explanations. Make sure you note down the lesson and then revise the collection every other day.
All the best!