How do you report a yes/no question in Spanish?

Use si (whether/if). A direct yes/no question like ¿Tienes hambre? becomes Me preguntó si tenía hambre. The si introduces the reported question and the verb backshifts exactly as in reported speech - present tienes to imperfect tenía after a past reporting verb. Do not confuse this si with the conditional si of if-clauses; here it simply means whether. There is no question mark on the reported version because it is no longer a direct question.

Do reported open questions keep the written accent on the question word?

Yes. Dónde, cuándo, qué, quién, por qué and the rest keep their written accent in a reported question just as in a direct one, because they are still interrogative: Me preguntó dónde estaba, Me preguntó por qué no había venido. What changes is the word order - Spanish drops the subject-verb inversion, so it is dónde estaba el tren, not estaba dónde el tren with the inversion English keeps. The accent stays; the inversion goes.

How do you report a command in Spanish?

Turn the imperative into que plus the imperfect subjunctive. A direct command like ¡Ven! becomes Me dijo que viniera (he told me to come), and a negative command like No salgas becomes Me dijo que no saliera (he told me not to go out). The imperative form itself disappears - it cannot be reported directly - and the imperfect subjunctive carries the instruction, after a past reporting verb such as me dijo, me pidió or me ordenó.

Reported Questions and Commands in Spanish

Reported speech handled statements: dijo que estaba cansado, with the tense sliding back one step. Questions and commands report the same way, with the same backshift, but each adds one move of its own. A question needs a word to introduce it; a command cannot keep its imperative and has to borrow the subjunctive. This page covers both.

Everything here assumes the backshift table from reported speech. If dijo que estaba and dijo que había llegado are not yet automatic, read that page first and come back.

Reported yes/no questions: si

A yes/no question - one that could be answered "yes" or "no" - is reported with si (whether / if).

"¿Tienes hambre?" -> Me preguntó si tenía hambre. (He asked me if I was hungry.)
"¿Quieres café?" -> Me preguntó si quería café. (He asked me whether I wanted coffee.)
"¿Has terminado?" -> Me preguntó si había terminado. (He asked me if I had finished.)

The verb backshifts exactly as in reported speech: tienes to tenía, has terminado to había terminado. The si does the introducing, and the question mark disappears, because the reported version is no longer a direct question.

This si is not the si of if-clauses; it just means "whether". Context keeps them apart: Me preguntó si venía (he asked whether I was coming) versus Si vienes, te ayudo (if you come, I'll help you).

Reported open questions: keep the question word

An open question - one that starts with a question word - keeps that word in the report. Qué, dónde, cuándo, por qué, quién, cómo, cuánto all carry straight over, and crucially they keep their written accent, because they are still interrogative.

"¿Dónde está el tren?" -> Me preguntó dónde estaba el tren. (He asked me where the train was.)
"¿Por qué no has venido?" -> Me preguntó por qué no había venido. (He asked me why I hadn't come.)
"¿Cuándo empieza la película?" -> Me preguntó cuándo empezaba la película. (He asked me when the film started.)
"¿Qué quieres?" -> Me preguntó qué quería. (He asked me what I wanted.)

The one thing that changes is word order. A direct question can invert subject and verb; the reported version drops the inversion and keeps the natural statement order.

Direct: ¿Dónde está el tren? Reported: Me preguntó dónde estaba el tren. - not dónde estaba el tren with any extra inversion.

So the rule for open reported questions is: keep the question word, keep its accent, drop the inversion, backshift the verb.

Reported commands: que plus the imperfect subjunctive

A command cannot be reported in the imperative - there is no "me dijo ven". Spanish turns the imperative into que plus the imperfect subjunctive.

"¡Ven!" -> Me dijo que viniera. (He told me to come.)
"¡Estudia más!" -> Me dijo que estudiara más. (He told me to study more.)
"¡Siéntate!" -> Me dijo que me sentara. (He told me to sit down.)

A negative command works the same way, with the no kept:

"No salgas." -> Me dijo que no saliera. (He told me not to go out.)
"No hables." -> Me pidió que no hablara. (He asked me not to talk.)

This is the indirect-command pattern you met with the subjunctive of wishes and influence: decir, pedir, ordenar, rogar plus que plus a subjunctive. In the present that subjunctive would be present (me dice que venga); after a past reporting verb the backshift pulls it to the imperfect subjunctive (me dijo que viniera). The same sequence-of-tenses rule that governs reported statements governs reported commands.

The reporting verb here is one of command or request - me dijo que, me pidió que, me ordenó que, me rogó que - not me preguntó, which belongs to questions. Choosing the right reporting verb is half the job: preguntar for questions, decir / pedir / ordenar for commands.

Worked examples

"¿Estás listo?" -> Me preguntó si estaba listo. (He asked me if I was ready.) - yes/no, si.
"¿Cuánto cuesta?" -> Me preguntó cuánto costaba. (He asked me how much it cost.) - open, keep cuánto.
"¿Por qué llegas tarde?" -> Me preguntó por qué llegaba tarde. (He asked me why I was arriving late.) - open, keep por qué.
"¡Llámame!" -> Me dijo que lo llamara. (He told me to call him.) - command, imperfect subjunctive.
"No te preocupes." -> Me dijo que no me preocupara. (He told me not to worry.) - negative command.
"Cierra la puerta." -> Me pidió que cerrara la puerta. (He asked me to close the door.) - command with pedir.

Common mistakes English speakers make

Using que instead of si for a yes/no question. Learners write Me preguntó que tenía hambre, mixing the statement que into a question. A yes/no question takes si: Me preguntó si tenía hambre. Save que for reported statements and for the command pattern.

Dropping the accent on the question word. Writing Me preguntó donde estaba loses the interrogative accent. In an indirect question the question word stays interrogative and keeps its accent: Me preguntó dónde estaba. The accent does not depend on the question mark.

Keeping English-style inversion. Producing Me preguntó dónde estaba él el tren or any inverted order copies the direct question. The reported open question uses statement order: Me preguntó dónde estaba el tren.

Trying to report a command with an imperative or an infinitive. Writing Me dijo ven or Me dijo venir misses the construction. The imperative cannot survive the report; Spanish needs que plus the imperfect subjunctive: Me dijo que viniera.

Leaving the subjunctive in the present after a past reporting verb. Producing Me dijo que venga clashes a past frame with a present subjunctive. The backshift applies: Me dijo que viniera. Sequence of tenses pulls the subjunctive back just as it pulls the indicative back in reported statements.

Get the three introducers straight - si for yes/no, the question word for open questions, que plus the imperfect subjunctive for commands - and reported questions and commands are just the backshift you already know, wearing a different opening word.