Subject-Verb Agreement
Wrong: The group of monkeys crowd around the tourist.
Right: The group of monkeys crowds around the tourist.
Wrong: Leading the pack is my mother and I.
Right: Leading the pack are my mother and I.
Verbs Tenses
Past Past Perfect
I walked to the store. I had walked to the store.
Present Present Perfect
I walk to the store. I have walked to the store.
Future Future Perfect
I will walk to the store. I will have walked to the store.
Keep verb tense the same throughout a sentence.
Wrong: After he has pulled me over, the cop asked for my ID, and I hand it over.
Right: After he had pulled me over, the cop asked for my ID, and I handed it over.