How do you form the pluperfect in Spanish?

Take the imperfect of haber and add a past participle. The auxiliary runs había, habías, había, habíamos, habíais, habían - note the written accent on every form. So hablar gives había hablado, comer gives había comido, vivir gives había vivido. The participle never changes for person or gender in a compound tense, and nothing may come between haber and it: pronouns and negatives sit in front (no lo había visto). The irregular participles carry over: había hecho, había dicho, había visto, había puesto, había escrito, había vuelto.

What is the difference between the pluperfect and the preterite?

The preterite reports a past event in its own right - llegué, I arrived. The pluperfect reports an event that was already complete before that past moment - había llegado, I had arrived. In a single sentence they stack: cuando llamaste, ya me había ido (when you called, I had already left) - the calling is the past reference point in the preterite, the leaving is the earlier past in the pluperfect. If two past actions happen in sequence with no 'earlier than' relationship, you use two preterites (entré y me senté); the pluperfect is only for the one that happened before the other.

When do you use the pluperfect with ya and todavía no?

Ya (already) and todavía no / aún no (not yet) are the pluperfect's most natural companions, because both measure one past point against an earlier one. Cuando el tren salió, ya habíamos subido (when the train left, we had already got on). Eran las diez y todavía no había llegado (it was ten and he still had not arrived). The pluperfect sets up the 'by then' frame - by the time X happened, Y had / had not yet happened - and ya / todavía no mark which side of it you are on.

The Pluperfect

The pluperfect - el pluscuamperfecto - is the tense for the past before the past. You are already narrating in past time, and you need to point at something that had already happened by then. English calls it "had done"; Spanish builds it as había plus a past participle. Cuando llegué, ya había salido - when I arrived, she had already left.

It is a compound tense, so it is formulaic: the auxiliary haber plus a past participle, and here the auxiliary sits in the imperfect. This page assumes you can already build the imperfect and that your participles - hablado, comido, vivido, hecho, dicho, visto, puesto, vuelto, escrito - are solid.

Building it: imperfect of haber + participle

One line. Take the imperfect of haber and add a past participle.

Person	haber (imperfect)	+ hablado
yo	había	había hablado
tú	habías	habías hablado
él / ella / usted	había	había hablado
nosotros	habíamos	habíamos hablado
vosotros	habíais	habíais hablado
ellos / ellas / ustedes	habían	habían hablado

So había comido (I had eaten), habías venido (you had come), habíamos hecho (we had done), habían dicho (they had said). Three things to fix. Every form of the auxiliary carries a written accent - había, habías, habíamos - because without it the stress falls wrong. The participle never moves: it is hablado for every person and both genders, since in a compound tense only the auxiliary conjugates. And nothing comes between haber and the participle - pronouns and negatives sit in front: no lo había visto, never "había no visto".

The irregular participles you already know carry straight over: había hecho (done), había dicho (said), había visto (seen), había puesto (put), había escrito (written), había vuelto (returned), había roto (broken), había abierto (opened).

What it means: a past inside a past

The pluperfect always looks back from a past reference point to something earlier. Picture two moments on the past-time line: a past reference point, and an action that was already finished before it. The finished-earlier action is the pluperfect.

Cuando llegué a casa, mi hermano ya había cenado. (When I got home, my brother had already had dinner.) - the arriving is the reference point (preterite); the dinner happened before it (pluperfect).
No entendí la película porque no había leído el libro. (I didn't understand the film because I hadn't read the book.)
Nos dijo que había estado en México. (She told us she had been to Mexico.)

Take away the earlier-than relationship and the pluperfect disappears. Two past actions in plain sequence take two preterites: entré y me senté (I went in and sat down). The pluperfect is reserved for the action that jumps behind the other one.

The pluperfect vs the preterite and imperfect

All three are past tenses, but they do different jobs, and the pluperfect is the only one that means "before another past".

Preterite - a completed past event, in its own time: llegó a las ocho.
Imperfect - an ongoing or habitual past state: llovía, siempre llegaba tarde.
Pluperfect - an event already finished before a past reference point: cuando llegó, ya había parado de llover.

Watch the three together:

Eran las nueve. Había llovido toda la tarde, pero ahora escampaba. Cuando por fin salí, las calles ya se habían secado.

It was nine (imperfect, the scene). It had rained all afternoon (pluperfect, finished before "now" in the story). It was clearing up (imperfect, ongoing). When I finally went out (preterite, the event). The streets had already dried (pluperfect, finished before I went out). Each tense earns its place.

Its natural companions: ya, todavía no, nunca, antes

Certain adverbs almost summon the pluperfect, because they compare one past point to an earlier one.

ya (already): Cuando el tren salió, ya habíamos subido. (When the train left, we had already got on.)
todavía no / aún no (not yet): Eran las diez y todavía no había llegado. (It was ten and he still had not arrived.)
nunca / jamás (never, up to that point): Era el mejor viaje que había hecho nunca. (It was the best trip I had ever made.)
antes (before): Nunca antes había visto el mar. (I had never seen the sea before.)

The pluperfect sets the "by then" frame - by the time X happened, Y had (or had not yet) happened - and these adverbs mark which side of it you are on.

In reported speech

When you report in the past what someone said, a present perfect or a preterite in the original often slides back to the pluperfect (see reported speech).

Direct: "He terminado." -> Reported: Dijo que había terminado. (He said he had finished.)
Direct: "Llegué tarde." -> Reported: Admitió que había llegado tarde. (He admitted he had arrived late.)

The backshift is automatic: a finished action, reported from a past vantage point, becomes pluperfect.

Worked examples

Cuando llamaste, ya me había ido. (When you called, I had already left.)
No sabía la noticia porque no había leído el periódico. (I didn't know the news because I hadn't read the paper.)
Nos habíamos conocido años antes, en la universidad. (We had met years earlier, at university.)
Para cuando llegó la ambulancia, el hombre ya había recuperado el conocimiento. (By the time the ambulance arrived, the man had already regained consciousness.)
Era la primera vez que había probado el pulpo. (It was the first time I had tried octopus.)
Me dijo que nunca había estado tan cansada. (She told me she had never been so tired.)

Common mistakes English speakers make

Forgetting the accent on haber. It is había, habías, habíamos with a written accent on every form. Dropping it (habia) is a spelling error and mispronounces the word.

Using the preterite where the pluperfect is needed. English is sometimes loose - "when I arrived she already left" - but Spanish is strict: the earlier action must be pluperfect. Cuando llegué, ya había salido, not "ya salió".

Splitting haber from the participle. Nothing goes between them. Pronouns and negatives sit in front of the whole block: no lo había hecho, ya se habían ido, never "había lo hecho".

Making the participle agree. In a compound tense the participle is invariable: ella había hablado, ellas habían hablado, las cartas que había escrito - always -o. Agreement belongs to ser/estar constructions, not to haber.

Build it from the imperfect of haber, use it for the action that was already over when another past moment arrived, and let ya and todavía no mark the "by then". That is the whole of the pluperfect.