Giving your opinion

I think that . . .

I don’t think that . . .

In my opinion . . .

Asking for support or details

Why do you think that?

Could you elaborate?

Could you give (me) an example?

Can you illustrate that?

What evidence do you have?

Could you explain it in more detail?

Could you provide some details?

Supporting your opinions

Let me illustrate,

For example,

For instance,

To give you an example,

Let me give you an example,

To elaborate,

First, (second), etc.

(These phrases can be followed by details, examples, elaboration, or a summary of your main points.)