When to use

Present (Presente)

Actions happening now, habits, facts

Preterite (Pretérito)

Completed action; one-time event

Imperfect (Imperfecto)

Habitual actions, descriptions, background information

Future (Futuro)

Will do; predictions

Conditional (Condicional)

Would do; hypothetical situations

Present Perfect (Pretérito Perfecto)

Have/has done

Past Perfect (Pluscuamperfecto)

Had done

Conditional Perfect (Condicional Perfecto)

Would have done

Present Subjunctive (Presente de Subjuntivo)

Emotion, doubt, influence, uncertainty in the present

Past Subjunctive (Imperfecto de Subjuntivo)

Emotion, doubt, influence, uncertainty in the past

Present Perfect Subjunctive (Pretérito Perfecto de Subjuntivo)

Emotion/doubt about something that has happened

Past Perfect Subjunctive (Pluscuamperfecto de Subjuntivo)

Emotion/doubt about something that had happened

Affirmative Command (Mandato Afirmativo)

Telling someone to do something

Negative Command (Mandato Negativo)

Telling someone not to do something

Indicative (Indicativo)

Facts and certainty

Subjunctive (Subjuntivo)

Feelings, doubt, uncertainty, wishes

Preterite

Picture (one completed snapshot)

Imperfect

Movie (ongoing background)

Future

Will

Conditional

Would

Present Perfect

Have done

Past Perfect

Had done

Conditional Perfect

Would have done

Indicative

Fact

Subjunctive

Feeling

Por

Reason, duration, exchange (backward-looking)

Para

Purpose, destination, deadline (forward-looking)

Ser

What something is

Estar

How something is

Preterite vs Imperfect

Story event vs story background

Present Subjunctive

Present emotion + que

Past Subjunctive

Past emotion + que

Affirmative Tú Command

Usually the él/ella form

Negative Tú Command

No + present subjunctive