To ensure that your baby receives both foremilk and hindmilk, it is important to let your baby finish with one breast before offering the second breast.
Do not interrupt or unlatch your baby if she is actively nursing and also do not time the feeds like they did in the old days (eg 10min per side).
Do not watch the clock when feeding, take your cue from your baby.
What I do with my daughter is the following:
1. I offer one breast and let her nurse until she unlatches herself (spits out the nipple), then I bring her up to burp her.
2. Then I place her back on the same breast to ensure she receives the hindmilk as well, I let her nurse until she unlatches herself again. Then bring her up to burp again.
3. If she is then still hungry / rooting (rooting is when your baby pecks around like a little bird on your chest in search of your nipple) I offer the second breast in the same manner.
Often she will only take one breast per feed. If she only took the one breast per feed, I will offer the other breast at the next feed. If she took both breasts, I will start her on the breast she drank from last at her next feed.
The duration of the nursing sessions will also become less as baby gets older and more efficient at getting the milk out. My little girl used to nurse for 40+ minutes at a time but now at 4 months it is down to 20 minutes.
However, the nursing sessions' duration does increase during growth spurts and wonder weeks.
Important to remember: Do not watch the clock when feeding, take your cue from your baby.