We often use 'suppose' to mean 'imagine' or 'guess'

• I suppose you'll be meeting Danielle when you go to Paris?
• When you weren't there, I supposed you must have been held up.
• I suppose you two know each other?

Notice that 'suppose' is not normally used in the continuous form. We do not usually say 'I am supposing'.

• Now I suppose we'll have to do something else.
• We're waiting for John and I suppose he must be stuck in traffic.
• At this moment I suppose it doesn't matter.

Notice that for 'imagine not' or 'guess not' that we make 'suppose' negative, not the other verb.

• I don't suppose you know where Mary is?
• I don't suppose he'll do anything.
• I don't suppose you have a Nokia phone charger here?

When responding to an idea with 'suppose', you can use 'so' to avoid repeating the idea that has already been expressed.

• Is Susan coming to this meeting? ~ -I suppose so.

'Supposed to be' can be used to mean 'it is said/believed'.

• The new James Bond movie is supposed to be excellent.
• He is supposed to have been rude to Mark but I don't believe it.
• It is supposed to be the best restaurant in town.

'Supposed to be' can also be used to talk about what is arranged, intended or expected. It is a bit like 'should'.

• I'm supposed to get to work by 8.
• John is supposed to turn off all the lights when he leaves.
• I'm supposed to pay my rent on the first of the month.

Often there is a suggestion that the action 'supposed to' happen does not actually happen

• I'm supposed to be there before 8 but I'm often late.
• You were supposed to phone me.
• I'm supposed to be getting on a plane to Tokyo at this very minute.

'Not supposed to' often suggest that something is not allowed or prohibited.

• You're not supposed to smoke in here.
• I'm not supposed to tell you.
• We're not supposed to use the Internet for personal reasons at work.

'Suppose' can also be used as a conjunction to mean 'what if'. Notice that the verb which follows it is sometimes, but not always, put 'more in the past'.

• Suppose we take the earlier train to Munich? It would give us more time there. ~ Suppose we took the plane instead? That would give us even more time.
• There's nobody in reception to let our visitors in. ~ Suppose I sit there until somebody comes?
• I'm going to ask him for a pay increase. ~ Suppose he said 'no'? What would you do?