Giving Advice - Language Point.

There are several different structures that you can use when giving advice 


Should: 

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


Had better :

This structure is common in spoken English and it is usually used inthe 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 


If I were you 


This version of the second conditional is often used when giving advice, especially in spoken English. Note the use of were with I in the first clause. 
In the second clause, we use would - contracted to d - and wouldn’t. 
After would and wouldn’t, we use the base form of the infinitive of the verb: 

If I were you, I’d give them back to the lecturer
If I were you, I wouldn’t use the answers