There are several different structures that you can use when giving advice
This is probably the most common of the structures for giving advice. After should, and its negative – shouldn’t – we use the base form of the infinitive of the verb:
You should wise up.
We shouldn’t cheat.
It is common to use ‘I think’ and ‘I don’t think’ with should:
I think you should put the answers back.
She doesn’t think they should use them.
This structure is common in spoken English and it is usually used in the contracted form. After had better, and its negative – had better not, we use the base form of the infinitive of the verb.
You’d better return the answers to the lecturer
You’d better not tell anyone that you found them
This is the most formal of the structures used for giving advice, and so it isn’t so common.
After ought, and its negative – ought not (oughtn’t), we use the full infinitive of the verb:
You ought to contact the police
You ought not to cheat in exams