1) When your parents are NOT holding an EV item, then the baby will get three random IV stats from both/either of the parents. The other 3 IVs are determined by the game randomly.
2) When the parent(s) are holding an EV item, then the baby will get the IV stat that the EV item boosts. For Example
Power Weight= HP
Power Band= Attack
Power Lens= Special Attack
My source would be, er, personal experience.