Here are some useful phrases to agree with others’ options:

• I agree with you 100 percent.
• I couldn’t agree with you more.
• That’s so true.
• That’s for sure.
• You’re absolutely right.
• Absolutely.
• That’s exactly how I feel.
• Exactly.
• No doubt about it.
• I was just going to say that.
• Yes, I agree …
• I think so, too.
• You took the words out of my mouth.
• That’s right/That’s true.
• That’s a good point.
• Great idea!
• (agree with negative statement) I don’t think so either.
• Me neither.
• Neither do I.
• (slang) Tell me about it!