(a) To ask for, beg, is translated pedir a.
He had slipped into the kitchen to ask the cook for something to eat.
Se había deslizado en la cocina para pedir algo que comer a la cocinera.—BLASCO IBÁÑEZ.
Note.—With pedir the thing asked for is the direct object, the person of whom it is asked is the indirect, and is introduced by a. Cf. English, "We begged a dollar from father."
(b) To ask in the sense of to request is rendered by pedir or rogar, the latter being the more formal. Both verbs require the subjunctive in the dependent verb.
I asked the children not to make so much noise.
Pedí a los niños que no hiciesen tanto ruido.
I asked Mr. Blanco to come and see me.
Le rogué al señor Blanco que me viniese a ver (a visitar).
(c) To ask, invite is rendered convidar or invitar.