Some people mistakenly think that Mexicans that set up ofrendas for their defunct relatives are actually worshiping them.  Nothing further from the truth. The vast majority of Mexicans are Christian Catholics, so they only worship God.

Ofrendas are set up to remember and honor the memory of their ancestors. Before setting an altar, they thoroughly clean their house. We must remember they are going to have very important “visitors”.

 The ofrenda is set on a table, covered with a fine tablecloth, preferably white. Then the papel picado, cut tissue paper, is set over the cloth.

Several levels can be set on the ofrendas. Generally, on the top level, the images of Saints and the Crucifix are set.
For each deceased relative, a candle is set. Their light is thought to guide them on their way back.
The light of the candles also called ceras -waxes- symbolize  Jesus Christ Reborn and faith.
Flowers, specially  Cempasuchitl, adorn the ofrenda.
Flowers represent the fugacity of life.

Salt and water are also essential; they are set to quench the thirst of the souls, tired from their long trip. Water also purifies and cleanses..

Incense, Copal, is burned and thought to elevate prayers to God

Pictures of the defunct are placed on the ofrenda, as well as some of their favorite clothing, perhaps a hat or a shawl.  For the children, they place small toys

Food is specially prepared for the souls. Their preferred dishes are cooked for them and placed on the altar: mole, tamales, fruits, arroz rojo -red rice-, hot chocolate and dried fruit. Some times cigarettes or liquor if the dead relative enjoyed them when alive. And of course Pan de Muerto.
It is important to mention that they will not eat the food, they only enjoy the aroma.

Sometimes a cross is made with petals of the cempasuchitl flower. Also with the petals, paths are set to guide the souls to the ofrenda.

Sugar Skulls: also known as calaveras/calaveritas. The same as Pan de Muertos, these symbolize the sweetness of life and death. Having sugar skulls at the ofrenda is representative of Mexican culture’s perspective on death, which tries to emphasize that death can be sweet. Sugar skulls are traditionally made of granulated sugar, chocolate, or amaranth and it is customary to have the deceased’s name written on the skull’s forehead to honor them, or have someone else’s name written on it and give it as a gift (children love them!). These sugar skulls can be found in many forms besides sugar such as clay, papier maché, and wood, so as to have them longer at the ofrenda and reuse in later years and/or for decoration.

In many towns, there are contests of ofrendas. Judges go house by house and elect the three most beautiful altars. Ofrendas are works of art, ephemeral art that is!