-a place to set up your altar (we used a wooden crate), whether it be a table, shelf, or any space that can contain and show off your items-think of this as a mini exhibit celebrating your passed loved ones.
-a picture of the deceased
-food (we placed a nectarine in our altar)
What each item means:
Candles: The purpose of creating an altar is both to celebrate the dead and to invite them back home, so lit candles are used to welcome them back.
Marigolds: Marigold flowers (cempasuchil) are used in altars for their scent, which guides the dead back home (supposedly, the scent of marigold flowers is reminiscent of bone, and that is why these particular flowers are used).
Water: Placing water on an altar helps quench the thirst of the dead, after their long journey home.
Sugar Skulls: Sugar skulls are an iconic memento mori placed on DoD altars. They represent both life and death, as they are placed on altars, but also given to the living.
Food: Because the dead will be hungry on their long journey home, it's fitting to add a few pieces of food. You'll see fruit, special bread (i.e. Pan de Muerto, or bread of the dead), and other snacks on many altars.
Papel Picado: Papel picado banners are festively strung across Day of the Dead altars.
Additionally, items belonging to the deceased or items they liked, small skeleton figurines, and other items are placed on a Day of the Dead altar. Here are examples of some awesome altars: