Santeria (la Regla de Ocha, la Regla Lucumi) is a cuban religion.
The slaves kidnapped from west-africa (mainly Yoruba from what is known Nigeria today), brought with them their beliefes into the new world and hid their Orishas under the cloak of catholic saints. In this way their religion could survived until today.

The followers of Santeria believe into a highest spiritual force called Olodumare. Olodumare is the source of spiritual power/energy which is called Aché. Because Olodumare is that far from humans, the Orishas mediate between that force and the human worlds.
To contact the Orishas the followers use rituals, prayers, oracles and sacrifice. In that way the Orishas are able to help solving problems and to support walking a spiritual path.

In the religion of Santeria there are different initiation levels someone could pass.
At the start is the search for a spiritual parent (madrina or padrino) who has to be a priestess/priest with her/his own ilé (house/temple). When you find the right person you could become a member of that religion. The first step is the receiving of mostly five necklaces (Ilekes) made of glass beads in different colors, which belong to five Orishas (Eleggua, Oshun, Yemaya, Chango, Obatala).

If it is in your spiritual path (oracle) you will get the warriors (guerreros) next. The warriors is a set fo four Orishas (Eleggua, Ogun, Ochossi, Ossun) which will help you to overcome difficulties on your path and protect you.
If you want to become a priestess/priest you have to pass the kariocha-ceremony, but only if the Orishas will allow you (oracle).

Before entering to that ceremony you must know the master of your head, your Orisha-parent. To find out you need to pass a ceremony done by the priests of Ifa/Orunla/Orunmila (the Orisha of oracle), the Babalawos. Mostly the Mano de Orunla ceremony (Hand of Orunla) is done for this purpose. This ceremony lasts three days and during this time you will be told your Orisha-parent and your destiny (life-oracle). You will get a complete set of three warriors in case you never got them. You will also get a small container which contains the "Hand of Orunmila" together with a necklace (Ileke) and a bracelet (idé) with the colors of Orunmila.

In case it is your destiny to become a priestess/priest in this religion you have to pass the kariocha-ceremony which wil last for seven days. During these days your are not allowed to leave the ritual room.
Before entering that room you will be led to the river to have a small ritual done there for Oshun. Later you will be initiated (born again), your head will be shaved completely and you will be dressed into white clothes. Also the Orishas will be put into your head.
On the third day there will be an oracle to find out your duties as a priestess/priest and also the life-long tabus you have to follow.
On the seventh day you will be brought to the market place. After that small ceremony you are allowed to leave the ritual room on your own. You are now an Iyawo (a new born priest) and you have to follow certain tabus for the first year (the Iyawojaré). For the first three month you are not allowed to go out in the darkness alone (only with a priestess/priest attenting you. You have to cover your head, sit on a mat on the ground while eating, are not allowed to see inside a mirror. For the rest of the year you have to wear white always, are not allowed to touch other people or to take things direytly from them. You are not allowed to get drunken or use drugs, you have to avoid crowds and much more.
All these tabus are there to protect the Iyawo and to help her/him to get adjusted more better to the energy of the Orishas. From that point on you have a life long relationship with the Orishas and they will treat you the way you will treat them.