Have a very specific bedtime routine for both children. Although your newborn will have a less predictable schedule, he will settle in over the next few months. If you keep their bedtime routine consistent, you'll have fewer issues getting your children to sleep.
Since your children are different ages, chances are they will not go to bed at the same time. Once your first child has been put to bed, keep the room dark. Then, do any bedtime ritual with your second child in a separate room. When you put her to bed, use only a night light as harsh lights may wake your first child.
Finally, play soft music or white noise (a recording of ocean waves or rain works well) throughout the night. This will help drown out any noises your children make so they don't wake each other up during the night.
Elizabeth Pantley (www.pantley.com) is the author of eight parenting books, including: The No-Cry Sleep Solution. Based in Washington, Pantley is the president of Better Beginnings Inc. (a family resource and education company).