1. Asking for and giving opinions

2. Asking for opinion
What do you think (of …)? What do you reckon? How do you feel about …? What‘s your opinion/view on …? What are your feelings about …? Tell me your opinion/views on …

3. Giving your opinion
I think (that) … because … In my opinion / In my view / In my experience … Well, personally, … I believe (that) … I feel (that) … If you ask me, … To be honest, … Quite frankly, …

4. Agreeing and disagreeing
I agree with you. I couldn’t agree more. I feel that way too. I think so too.
(I’m afraid) I don’t agree with you. Yes, but on the other hand... I see your point, but... Could be, but... It may be true, but... I don’t think so. I disagree with what you’ve just said. I think that’s nonsense.