1.after words to advice, to ask, to command,to insist(настаиветь), to demand(требовать), to suggest,to desire,to propose(предлогать),to recommend, to request(просить), to urge(побудать) to require which involve an implied obligation, the subjunctive may be used in firmal style.This has only the one form,that of the infinitive,and there is no third person -s,or past form. The verb be has be for all forms.
They demanded that he leave at once.
the same applies after expressions such as it is necessary/essential/important/best/crucial(решаюше)desireble,imperative,recommended,urfent, vital,a good idea, a bad idea that...
It is essential that you arrive before six.
The subjunctives can be used in negative fiom,continuous and passive forms.
Negative The boss insisted that Sam not be a the meeting
Passive ex. Ann demanded that I be allowed to take part in the negotiations.
Continuous ex. It is important that you be standing there when he gets of the plane.
2.Less formal usage
Less formally, should can be used, and colloqualy no tense change is made,or an infinitiv constraction is used.
They emanded that he should leave.