It is important to understand when and how to use the subjunctive mood in English. The subjunctive is used to express necessity, urgency, or importance when stating a call to action or making a recommendation. It is also used after expressions of emotion like insistence, demand, or adamancy when suggesting something should or should not occur. The subjunctive can be formed using the infinitive without "to" or using a passive or gerund construction.

1. WHEN?
Urgency
Importance
 CALL TO A C T I O N
If you are stating a fact you CANNOT use
the subjunctive: It is important to
remember that Donald Trump is a half wit
Call to action: It is important that Donald
Trump keep doing what he does best…
Verbs and expressions lending themselves
to the use of the subjunctive:
It is urgent / crucial / vital / essential /
necessary / indispensable… THAT

2. To suggest / recommend / advise / insist /
demand / be adamant THAT
HOW?
The infinitive without TO
+  It is necessary that she learn her
vocabulary
-  It is vital that Marta C. NOT BE at the
party…
-  It is crucial that Jeanphi NOT FAIL
anyone
Passive  Mrs Finkelstein demands that
her heater BE REPAIRED
Gerund  My boss was adamant that I BE
WAITING for Mr Smith with a nice nominal
sign outside the airport lounge for as long
as it would take…