Making suggestions and giving advice: You should try to learn English everyday.
I think you should go home early.
Why don't you join an English club?
You'd better wake up early.
Let's have dinner together.
What about having a cup of coffee with me?
How about going to the cinema?
Don't you think it would be a good idea to have a picnic this Sunday.
If I were you, I'd call her.
I suggest that you take a nap.
You may want to try on this T-shirt.
Perhaps you could take an umbrella with you.
I strongly advise you to do more work out.
I recommend that you get some rest.
It's better for you to sleep a little more.
Accepting Suggestions:
Thanks, I'll do it.
It sounds good.
That sounds like a good idea.
Thanks. It's a good suggestion.
I think you're right.
Why didn't I think of that?
Refusing suggestions:
No, I'd rather not.
I don't think so.
I don't feel like it.
No, I don't this it's a good idea.
What a bad idea!
