The other half of the tense. Take off the -er or -ir ending and put -ía. Yes, the same sound as would.
comer → comía · vender → vendía
Comía · Lo vendía · Se vendía · Lo rompía · Se rompía · Se rompían
Both use -ía, so the difference is entirely in what you attach it to. For would you add it to the whole "to" form. For the past you strip the ending first.
Lo vendería / Lo vendía · Lo rompería / Lo rompía · Lo romperían / Lo rompían · Se vendería / Se vendía
Some of the most common signs you will see in a Spanish-speaking place are exactly this structure.
¿Cómo se dice? is the one to use when treating a friend as a dictionary. Do not say "¿cómo dices?", which asks how that individual personally says it.
As usual the "we" form escapes the irregularity, because the accent sits elsewhere, so it goes back to decir.
Another inverted structure, like gustar. I have one left is it remains to me one.
me queda uno (I have one left)
The verb agrees with the thing remaining, so two gives quedan. In a shop you may hear either no me queda or no me quedan, depending on what the speaker has in mind.
The se travels wherever the verb goes.
Se va a romper / Va a romperse · Se queda · Se quedan · Se quedaban · No se quedaban aquí · No me quedaba aquí · Nos quedábamos aquí · No nos quedábamos aquí
No nos quedaba, or no nos quedaban, for we didn't have any left.