Some verbs require the accusative, effectively having 2 direct objects:

Я попросил его подождать пару минут. (accusative + infinitive)
Я посоветовал ему подождать пару минут. (dative + infinitive)

The difference is completely up to the main verb. Попросить requires the accusative and посоветовать requires the dative. It is unlikely that there is a reasonable explanation for this, so you just have to remember required grammatical cases for each verb.