I did it whenever I could: Lo hacía siempre que podía. I could do it if I had the necessary means: Podría hacerlo si tuviese los medics necesarios.
"Would," meaning "used to," is, of course, translated by the imperfect indicative—
When he was in Paris he would sit in the cafés for hours: Cuando estaba en Paris se pasaba horas enteras en los cafés.
"Should he do," etc., is translated "if he should do," etc. (si lo hiciese).[197]
"If I were to go" is translated "if I went" (si fuese).
[Footnote 197: After si (if—Conditional) the verb is present indicative or imperfect subjunctive (see Lesson XXIV).]
"Can" is translated by saber when the faculty expressed is the result of learning, as—
Can you play the piano? ¿Sabe V. tocar el pianoforte?
"To be to," "to have to" are translated by Tener que, Haber de or Deber (see Lesson XXVII), as—
Who is to write out that invoice? ¿Quién ha de (debe) escribir aquella
factura?
I have to be very careful: He de ser muy cuidadoso.
I shall have to work hard: Tendró que trabajar fuerte.