There are actually some very clear-cut rules for when to use present subjunctive or imperfect subjunctive. It all depends on what tense is used in the main clause of the sentence.
SEQUENCE OF TENSES for subjunctive
|
Tense of main clause |
QUE |
Subjunctive tense in dependent clause |
|
PRESENT |
PRESENT SUBJUNCTIVE |
|
|
FUTURE |
||
|
COMMAND |
||
|
PRETERIT |
QUE |
IMPERFECT SUBJUNCTIVE |
|
IMPERFECT |
||
|
CONDITIONAL |
Espero que él venga al cine con nosotros.
Será posible que él venga al cine con nosotros.
Me alegró que él viniera con nosotros.
Yo dudaba que él viniera al cine.