Companies all have different definitions for business casual. If you have never been in the building to see what everyone else wears you should dress up not down. The first day at minimum I would wear a button up dress shirt, dress pants, slip on leather dress shoes. Maybe wear a tie if you wish. Bring some polos for the following days if everyone else is more relaxed. Sweaters are never out of style but I will never wear one. Don't ever wear jeans and shoes to work unless it is a "dress down" day.