I find it really hard to express myself in class. I have lots of ideas, but they never seem to come out of my mouth.
let me give you a little advice. You know what the topics are going to be, so prepares what you would like to say in advance.
I often do, but I'm worried about the responses from other people.
you have to be realistic. Not everyone is going to agree with you, but people will respect your opinion and they will respect the fact that you have contributed something to the discussion.
I'm worried that what I say will not make sense.
we could chat about the topic before class. I could check that what you want to say is logical and it would also give you a chance to practice speaking.
that's a good idea. What should I do if I am in two minds about a topic?
that's easy. Express possibilities. People will think that you are pretty smart to be able to look at the topic from more than one angle.
I didn't realize that speaking in class could be so easy.
the most difficult thing is being able to predict what other people will say. They will reply to your statements, but you can't be sure how.