Salma Hayek did not have a choreographer for her dance. Director Robert Rodriguez just told her to feel the music and dance to it. Rodriguez would later use the same tactic with Jessica Alba in Sin City (2005).
Originally, Satanico Pandemonium was called Blonde Death. Quentin Tarantino decided to go for a Latino/Mexican star, so he used Salma Hayek after seeing her in Desperado (1995). The name Satanico Pandemonium came from the title of a gory Mexican horror movie (Santanico Pandemonium: La Sexorcista 1975) that Tarantino had seen on the shelves of the video store he worked in.
Hayek has a real fear of snakes and had always refused to be near them. Naturally when she read the script, she knew her phobia would prevent her from taking the part. Robert Rodriguez conned her into thinking that Madonna was ready to nab the part instead so Hayek spent two months with therapists to overcome her fear.
From Dusk Till Dawn – Salma Hayek