Should,Should not and forms for giving advice.
a_____do not you ask that man for directions?
b You____try to speak English as much as possible in class.
c_____ putting a little salt in yhe water: it`ll taste much better.
d You____worry so much. I`m sure everything will be OK.
e____I go to the hairdresser`s or not? What do you think?

Why don't you ask....You should try to speak.....Try putting a little salt....You shouldn't (should not) worry so much....Should I go ....