Starting with a topic sentence

A standard paragraph starts with a topic sentece, which ...

is usually a rather general statement
has a direct, clear message (choose verb accordingly!)
signals the kind of paragraph that will follow (an explanation, a list of examples, a definition of the problem ...)
often asks or implies a question and promises an answer

Examples

Topic sentence	The reader thinks:
I am clearly against a speed limit for several reasons!	What are these reasons?
There can only be three possible answers the British government may give.	What are these answers? Why can there only be three?
The events of last week were a terrible blow for those who love their freedom.	What happened?
It seems unbelievable, but there is no way to save Tibet's cultural heritage.	Why is it not possible?