Snacking throughout the day is an important activity for a pet parrot, so it is important to train your person to provide you with snacks as needed. For example, if you happen to come across a bowl of tangerines on the table, you should stand and stare at them. If that doesn't get your person's attention, then touch a tangerine with your beak. If that doesn't do the trick, then just use your beak to start peeling the tangerine yourself. That way your person will surely understand that it is time to peel the tangerine for you and offer you as many slices as you like.
As every pet parrot knows, the best place to eat a tangerine slice is on you person's shoulder.