You are certain of your opinion:
I'm certain that...
I'm sure that
It's my opinion that...
I'm convinced that...
I honestly believe that...
I strongly believe that...
Without a doubt...
I'm positive...
I'm absolutely certain/convinced
that...
to emphasize that what you are going to say is your own opinion:
In my opinion,...
I personally believe...
I personally think...
I personally feel...
Not everyone will agree with me, but...
In my opinion,...
From my point of view,...
Well, personally,...
In my case...
Well, as far as I can see
as far as I'm concerned
Well, I think / I'd say
If you ask me,
If you want my opinion,
I have the feeling that
Personally speaking, I
think...
Agreeing with an opinion
I (quite) agree.
I agree completely / entirely.
I couldn't agree (with you) more.
I entirely agree with you (about/on that).
That's true / right/ just
Quite / Exactly / Precisely / Right.
That's true / right / just it.
I think so, too.
I don't think so, either.
Yes, that's right.
Yes, you're quite right.
Yes, exactly / of course.
That's exactly what I meant/say.
Yes, that's just my feeling / opinion.
how I see it.
That's how I feel (about it,
too).
Polite disagreement
I disagree with (you), I'm afraid.
No, I really can't agree,
I don't quite agree here.
Do you really thinks so / believe that?
You don't really mean that, do you?
I wouldn't say so.
Don't you think (perhaps)...?
Strong disagreement
I don't want to argue with you, .......
You're wrong, you know.
You're not serious - surely!
(Stop.) That's not correct.
(Oh,) You don't understand, I'm afraid.
That's not true / fair.
I can't accept your view that
I doubt if...
I disagree entirely.
Oh, come on! You must be joking! You can't be
serious!