What works for me:
Grammar Fundamentals: Master basic grammar rules such as subject-verb agreement, parallelism, pronoun usage, modifiers, and idiomatic expressions commonly tested in GMAT sentence correction.
Read Actively: Pay attention to the entire sentence structure, not just the underlined portion. Context often reveals errors outside the highlighted text.
Eliminate Distractions: Disregard non-underlined parts and focus solely on the underlined section. Avoid being swayed by the surrounding text.
Use Process of Elimination: Eliminate answer choices with obvious errors first. Then, examine remaining options for more subtle mistakes, ensuring the selected choice corrects the error logically and maintains the intended meaning.