Hello Alice,
You can use should or had better to give advice to someone.
But had better is used for more urgent advice with possibly bad consequences if you don't follow it. It is a kind of warning or even a threat.
Examples: - "You should see this movie!" I think it would be a good thing for you if you see the movie because it is a very good one.
- "You had better do your homework!" I think if you don't do it, it would be bad for you. You can specify the consequences in your sentence: "You had better do your homework, or you will fail the test"
Had better is often contracted in 'd better: "You'd better quit smoking."
I hope my answer helps you,
Phil