Wah How to use "Supposed to".

We can use supposed to to indicate obligation.
We usually use this form in an unfulfilled or angry way.

Be + Supposed to + Verb

It is similar to should and ought to.

• You are supposed to be at work. (You should be at work.) 
• You are not supposed to smoke here. (You should not smoke here.)
• I am not supposed to be here. Please don't tell anyone.
• You are supposed to introduce yourself.
• Are you supposed to know that? 
• What am I supposed to do?

We can use supposed to to indicate obligation in the past.

• I was supposed to go to work yesterday. (But I didn't.)
• How was I supposed to know that? (No one told me about that.) 
• You were supposed to clean your room.
• He was not supposed to tell you.
• Sally was supposed to meet her friend last night.

They are supposed to study hard for the exam tomorrow.

Wah How to use "Had better"

You can use had better or had better not to give suggestion or advice to someone.

Had better + verb

I had better go now. I had better to go now is incorrect.

1. Had better is similar to should but we use had better for giving strong advice which is quite serious if you do not follow it.

    You had better study hard for this examination. 

    (You should study hard for this examination.)

    You’d better go to bed right now if you don’t want to be drowsy tomorrow.    
    (You ought to go to bed right now)

2. You can also use had better when you think it is a good idea to do something.

    You’d better not to be late in English class. 

    (It’s not a good idea to be late.)

    The traffic is very bad today; we’d better go to the Wasabi Park by train.

    Hadn't we better be at the Central Park now, John have been waiting for us. 

Wah How to use "Should"

Should is a modal auxiliary verb. It is used to express the speaker’s opinion at the moment of speaking

Affirmative           

• I should go.
• He should go.

Negative

• I shouldn't go.
• He shouldn't go.

Interrogative

• *Should I go?
• Should he go?

*Questions with Should I / we …?  are unusual.We usually say..

Wah How to use "Ought to"

You can use ought to to give advice or tell someone what to do.

• You ought to go to bed early. (You should go to bed early.)
• Ought we to have lunch now? (Do you think it's a good idea for us to have lunch now?)
• We oughtn't to leave this door unlocked.

Ought, like should, is a modal verb:
It does not take an -s in the third person. (oughts)
There is no past tense or gerund. (oughted,oughting)