Thunderclan has very private burials. It is exclusive to only the direct family of the deceased cat and the Leader. When a cat is buried, their loved ones select a trinket (example: a flower, item from the Twoleg Place, lock of fur) to toss into the grave for the deceased cat to take to the afterlife. The Leader and the family members will go around and say a few words about the deceased cat before covering their grave. If the family members of the deceased cat can locate their grave, it is considered good luck. However, if they cannot locate their grave, it is considered bad luck.
When a high-ranking cat (example: a Leader or Medicine Cat) dies, a feast is thrown in their honor by the clan. The cats typically say a few kind words, or share a favorite memory they had with the fallen cat.