Here are a few quick tricks I like to use when Sentence Correction starts to feel overwhelming (especially when dealing with convoluted meanings, extremely bloated, wordy clauses, and completely-underlined sentences):
1. Mentally “remove” appositive phrases.
Long GMAT sentences often have way too much extra information. Try to mentally delete the useless info, and hone in on the main pieces of the sentence.
2. Listen to your gut.
Your accuracy was better when you were instinctually identifying what “sounded funny” to you. Hone in on that. The point of learning the common errors is to have a mental checklist to go through when you CAN’T identify what “sounds funny”.
3. Start by identifying the Subject & the Verb.
Every sentence must have them, and if you start here, you’ll be less likely to be overwhelmed by the sentence as a whole.