Sam's supernatural abilities are the result of him being fed Azazel's demon blood while he was an infant. Sam exhibits signs of precognition throughout the first season, manifesting as dreams of others' deaths and later as visions.

It gave Sam special powers . Ruby (brunette, not blond), under orders from Lilith, got Sam addicted to demon blood. Ruby told Sam that the blood would boost his power (it did) in order for him to have strong enough power to defeat and kill Lilith (he did).