Volume 2, Book 15, Number 771:
Narrated Anas bin Malik:
Allah’s Apostle never proceeded (for the prayer) on the Day of ‘Id-ul-Fitr unless he had eaten some dates. Anas also narrated: The Prophet used to eat odd number of dates.
Note that this Sunnah is for Eid-ul-Fitr only. The one that comes after Ramadan. :)
Eat dates before leaving for prayer, and that too in an odd number. 1, 3 , 5, 7…