For things that are important and necessary to do we use...
For something that is not advisable we use...
For things that are not essential we use...
For rules and regulations we often use...
When it is important and necessary NOT to do something we use...
For something that is advisable we use...
mustn't, can't
have to, need to, must
should
don't have to, don't need to
have to, must
shouldn't