There are three ways to use the subjunctive.
First is with 'wish'; off the top of my head, 'wish' is the only word that uses this form.
I wish that he were here.
I wish that I had a million dollars
Use wish, that, and the past tense of the verb; if using 'to be' as the verb, always use were, regardless of the plurality of the object. This expresses contrary-to-fact desires
Second is the conditional.
If he were here, I would be happy.
If I had a million dollars, I'd buy you a fur coat.
It uses if, were (or rarely another past-tense verb), and would, to express a condition and a consequence that are both contrary to fact.
Third is demands, requests, and suggestions.
I recommend that you work hard every day to prepare for the GMAT.
I suggest that you avoid real fur coats. They're cruel.
They use a word indicating an imperative to act in a contrary-to-fact manner, the word 'that', and the bare infinitive of the verb.