When to pump?

I'm a FTM due soon and plan on breast feeding. I have a breast pump and would like to use it so my husband could feed our daughter at times too. My question is when do you pump your milk? Doesn't the milk come in and you feed it to your baby? I don't want to pump and then not have any milk in my breasts when she is hungry. I'm just confused on how to start a pumped milk supply, yet still have milk available in my breast when she is hungry at a given moment. Any advice?