你认为英语怎么说？

what do you think..........?

What do you think about (the plan)?你认为(这个计划)怎么样?
Do you think it will rain?你认为会下雨吗?
Yes,I think so 我认为/看会的.
I think myself very lucky.我认为自己十分幸运.
I deemed it my duty to help.我认为助人是我的责任.

How can I speak it in English?
或者In your opinion,what is it?