You should see a doctor about that cough. (ought)
You ought to see a doctor about that cough.
All visitors have to have a visa. (compulsory)
It's compulsory for all visitors to have a visa.
It's against the rules to use mobile phones in this area. (allowed)
Using mobile phones in this area is not allowed / You're not allowed to use...
You are obliged to keep to the speed limit. (must)
You must keep to the speed limit. / You mustn't break the speed limit.
You should hurry up before the shops close. (better)
You'd better hurry up before the shops close.
"Do I need to take notes?" "You decide." (up)
It's up to you.
The sign says there's no parking in this street. (supposed)
You're not supposed to park in this street.
It's not necessary to wear a uniform when learning online. (need)
You needn't wear... / You don't need to wear a uniform...