Is there a certain ritual you must go through in order to become a witch?
Witchcraft consists of many traditions. Each has its own requirements. Our coven works on a three degree system. First there is a ceremony in which you are linked to the coven for a period of time. This period is used to learn about the Craft and to see if you and the coven mesh. If all works out, you are initiated into the First Degree. The Second Degree and Third Degree may come later and each has its own ceremony. Many solitary witches perform a self dedication rite by themselves and refer to themselves as witches there after. This is equally as valid. Ray Buckland's Complete Book of Witchcraft and Scott Cunningham's Wicca: A guide for the solitary practitioner, not only have dedicatory rituals, but contain a complete set of most witch celebrations. If you are doing this by your self, either book will do. If you are working with friends, the Buckland book may be a little better. We highly recommend both. See the Suggested Reading List for more information and additional books.
Some witches insist that you are only a true witch if you are initiated into a coven by an actual High Priest or Priestess. While it is their right to believe this, the vast majority of the Craft community do not hold this view. The majority will recognize your self dedication and consider you a real witch. For those others I ask, who initiated the first witch?
If you really aren't religious, but you have a religion, is it betraying the religion if you become a witch?
This is a matter of opinion and not an easy question to answer. Many people would tell you that yes, it is betraying your religion. Ultimately what is most important is what you believe, and not what other people tell you to believe. Listen to your heart. Most witches were brought up in other religions, therefore we, as a group, don't believe it is betrayal. However, we would never try to push our beliefs onto you.