This document discusses the differences between using "had better" and "should" when giving advice. It notes:
1) "Had better" is used to give advice about specific present or future situations using the infinitive without "to". "Should" is used for more general advice.
2) "Had better" implies there may be negative consequences if the advice is not followed, while "should" does not have this implication.
3) Both "had better" and "should" can be used to give advice about specific situations, but "had better" suggests something bad will happen if the advice is not taken.