Baby Sleep: Helping Infant Self-Soothe
Even very young infants can be placed in their beds when drowsy but not fully asleep, so that they can learn to settle themselves and go to sleep. I recommend that parents start doing this as early as possible, much earlier than 6 months. Of course, everyone enjoys rocking an infant at times. It is one of the finer things in life. Just be careful not to rock your baby to sleep every time she goes to sleep. If you do, she'll never learn to go to sleep on her own.
It's also important not to put the baby in bed with a bottle. She will quickly get into the habit of always needing a bottle to go to sleep. Also, babies can develop severe cavities because milk coats the teeth and bathes them in sugar. Finally, I don't recommend putting your baby in bed with you just so that she will get to sleep. In the short term, the baby may sleep, but it does not build good sleep habits.
If you do find yourself in the situation of having a child with poor sleeping habits or a disrupted sleeping pattern, there is help. After 6 months of age, but not before, there are other methods to help babies sleep. Make sure the baby is sleepy, fed, dry, not sick, etc. Then, place the baby in the bed, drowsy. Leave the room to allow the baby to calm herself. Most likely, the baby will cry. Return to the room in five minutes. Reassure yourself that the baby is OK. Do not change the diaper, hold the baby, rock the baby, etc. The baby may cry longer and louder when the parent is in the room. Go into the room every five minutes to check on the baby. The next night, do the same thing, but don't go into the room until after 10 minutes. On the third night, go in after 15 minutes. On the forth night, after 20 minutes, fifth night after 25 minutes, etc. This can be difficult, but your baby will learn to settle down independently.