-I agree with you 100 percent.
-I couldn't agree with you more.
-That's so true.
-That's for sure.
-That's exactly how I feel.Exactly.
-I'm afraid I agree with James.
-I have to side with Dad on this one.
-No doubt about it.(agree with negative statement) Me neither
-I don't think so.
-I'm afraid I disagree.
-I beg to differ.
-That's not always true.
-That's not always the case.
-No, I'm not so sure about that..