Past wishes, polite requests and indefinite antecedents
You met tuviera/fuera inside conditionals. The imperfect subjunctive also follows any past-tense trigger: quería que, esperaba que, me pidió que.
Quería que vinieras a la fiesta. (I wanted you to come to the party.)
Esperaba que el examen fuera más fácil. (I hoped the exam would be easier.)
The rule of pairs: present trigger → present subjunctive (quiero que vengas); past trigger → imperfect subjunctive (quería que vinieras).
From the ellos-indefinido minus -ron: hablara, comiera, viviera. Every form has a -se twin with identical meaning.
dijeron → dijera / dijese · quisieron → quisiera / quisiese
fueron → fuera / fuese · hubieron → hubiera / hubiese
Literature loves -se; conversation prefers -ra. Use -ra, recognise both.
When the person or thing you describe may not exist, the relative clause takes the subjunctive.
Busco un piso que tenga terraza. (I'm looking for a flat that has a terrace — any such flat, maybe none.)
Compare: Vivo en un piso que tiene terraza. (I live in one — it exists, indicative.)
No hay nadie que lo entienda. (There's nobody who understands it.)
Known and real → indicative. Hypothetical or denied → subjunctive. This contrast is a B2 exam favourite.
The imperfect subjunctive of querer doubles as ultra-polite "I would like": quisiera.
Quisiera hacer una reclamación. (I would like to make a complaint.)
Quisiéramos una mesa junto a la ventana. (We would like a table by the window.)
Quisiera outranks querría in formality — perfect for complaints, hotels and officialdom.
Ojalá's meaning shifts with the tense that follows it.
Ojalá venga. (I hope he comes — possible.)
Ojalá viniera. (I wish he would come — unlikely.)
Ojalá hubiera venido. (I wish he had come — impossible now, pure regret.)
Three tenses, three degrees of hope: venga (hope) → viniera (wish) → hubiera venido (regret).
Traps for English speakers
These are the errors English speakers make most often.