Dana Yost, who plays Mi in the film, is actually blindfolded while on screen. She relied on small gaps of light underneath the blindfold, as well as the thin material used for it, to see what was going on around her.
Though it may not look like it, that is a real snake sitting outside of Chow Lu Fong's home. It, along with two or three others, happened to be hanging out by the door during filming.