Sheikh `Abd al-Wahhâb al-Turayrî, former professor at al-Imâm University in Riyadh
The Muslim should, when offering his supplications to his Lord, ask for good for his or her self, for parents because of their favors on the supplicant, for whoever did something good for the supplicant, for all Muslims, and then the supplicant also pray to Allah to grant all people in the world guidance.
However, this is not obligatory, though it is one the highly recommended acts. The only supplications which are obligatory are the ones which are specifically prescribed during prayers and other formal acts of worship.
Source: Islam Today