It's usually seen that when you have an opinion, you can use some normal expressions like:
- In my opinion, ...
- I think that ...
- In my point of view, ...
- To me, ...
These functions are widely used in both speaking and writing [ because they're easy to remember ^_^]. But using different functions to show your opinion may make your essays, your speeches more vivid and clear. This also prevent readers or listeners from feeling bored. You certainly don't want the readers or the listeners to read or hear the same expression: " In my opinion,..." every time you give out a new idea, right ? So try to use some other expressions:
+ Informal : - If you ask me ...
- I'd say that ...
- The point is ...
- As I see it ...
- I'd just like to say that I think that ...
+ Formal: I'd like to point out that ...
In addition, sometimes you need to show others how you feel about what they are saying, keep in your mind that you should always be polite when you disagree with them even though they might be your close friends.

+ Agreement: - I can't agree with you more ! [strongest]
- That's just what I was thinking.
- I agree entirely.
+ Disagreement: - Yes, that's quite true, but ...
- Well, you have a point there, but ...
- I see what you mean, but ...
* The following functions are used when you know the person speaking very well, but in my opinion, you'd better not use them in any cases:- Come off it!
- Don't be silly!
- You can't be serious!
If you don't want to strongly present your opinions because you don't want to start an argument. Here are some expressions that might be useful:
- I sometimes think that ...
- Would you agree that ... ?
- Do you think it's right to say that ... ?
If you do not clearly understand what someone 's talking about and want them to explain more, you can use the following expressions:- I don't quite follow what you're saying about
- I don't quite see what you mean, I'm afraid.
- I don't quite see what you're getting at.
And if someone don't understand what you're saying, you may need the following expressions to rephrase your statements:
- That's not quite what I meant...
- Let me put it another way...
- Sorry, let me explain ...

Phew, I've just introduced some expressions that you might find useful in a discussion or a debate . Hope you'll find them useful. [Mr Violence]
http://www.telegraph.co.uk/news/graphics/2008/03/29/npolitics229.jpg
http://www.baronhats.com/images/gatsby-idea!.jpg
http://www1.istockphoto.com/file_thumbview_approve/236674/2/istockphoto_236674_agree_2.jpg
http://www.businessinnovationinsider.com/images/2006/03/Question%20Mark.jpg
http://picasaweb.google.com/canonsnaps/AirForceAndI/photo#4988400447734022162
http://www.reading-sfl.org.uk/images/workshop04/Discussion.jpg




A picture for Mr Photographer he he