1) I seen vs. I saw Incorrect: “I seen the movie last week.” Correct: “I saw the movie last week.”
2) I been vs. I have been Incorrect: “I been there!” Correct: “I have (I’ve) been there!”
3) I done vs. I did Incorrect: “I done the homework.” Correct:”I did the homework.”
4) We was vs. we were Incorrect: “We was just about to start the reading.” Correct: “We were just about to start the reading.”
5) I would of vs. I would have Incorrect: “I would of gone with you if I knew.” Correct:”I would have (would’ve) gone with you if I had known.”
Bonus: Be careful with past simple (I knew) and past perfect (I had known) constructions. Though they have similar meanings, it’s best to use the tense that matches the tense in the first part of the sentence (I would have). Match have/had constructions with have/had in clause pairs.