It's actually a very simple process. Mal ojo is usually associated with babies and used to explain an infant that is colic or feverish/vomiting. The baby is placed in a candle-lit room and a raw, unbroken egg is passed over its body (usually in the sign of the cross) while a prayer is recited in Spanish.

My grandmother also used to burn a mixture of herbs you can still buy in any Mexican market. After the baby was taken away, she would break the egg to study the contents. I can't explain how/why it worked, but it usually did. I have seen eggs broken that were reddish/black. She used to say it was the evil spirits from the baby. It was actually kinda freaky.