If you are exclusively pumping, you should pump every 2-3 hours, or as much as baby is eating. If you pump in addition to nursing, you should always pump whenever a bottle is given instead of breastfeeding. If you are trying to get some extra freezer supply, the best time to pump is in the morning - usually about 15-30 minutes after your first nursing session. It's a common misconception that you HAVE to pump in order to breastfeed. This is not true! If you have no reason to pump and baby is growing well from breastfeeding alone, don't feel like you have to pump. I pumped a grand total of two times with my oldest child, and I breastfed him until he was nearly two.