I'm supposed to arrive before the party starts.
It's supposed to be fun.
You aren't supposed to smoke in here.
She isn't supposed to yell at customers.
You're not supposed to smoke in here.
She's not supposed to yell at customers.
Are we supposed to bring gifts?
Am I supposed to take notes?
Aren't you supposed to take notes?
Isn't that movie supposed to be boring?
Note that the answer for a NEGATIVE QUESTION is assumed to be "yes." Sometimes this is used as a rhetorical question. For example, I know that you're supposed to take notes, and I'm actually just reminding you to do so. Other times, I'm fairly certain that the answer is yes, but I am still asking for your answer. For example, I heard from several people that the movie was boring, but I am still asking for your opinion.