1. Shall expresses certain laws and rules
You shall abide by the law.
Students shall not enter this room.
2. Something take place or exist in the future
a) We use shall for offers
Shall I pick you up from airport?
Shall we dance?
Shall I open the window?
What time shall we meet?
c) Future expression and promises
I shall be here at 7 tomorrow.
Should is the past tense of shall
1. We can use it as a personal opinion
You should go to the police.
You should see a doctor.
2. Use to express that we wish something had happened but it didn’t
You should have seen it, it was beautiful.
3. Should used to ask for someone’s opinion
What should we do now?
4. Used something expected or correct
Everybody should arrive by 6 pm.