In general, try to stick to activities and routines with your child similar to those you did before the baby arrived. Certainly you won't be able to do everything you did before or do it as much. But when you can't, try not to "blame" the baby—for instance, saying, "I can't because the baby needs…." Sometimes it will be unavoidable, of course. Your child will see that you are nursing or changing the baby and that's why you can't play with him. If so, own up to it, but promise your older child that he will get his turn with you soon.
If your child is in day care, alert your daycare providers that he may need special attention, a sympathetic ear, and pointed praise for a while as he adjusts to the new baby. And do the same for him at home.
Do everything you and your partner can do to set aside at least half an hour a day (each) to spend alone with your older child, giving him your full attention. Your special time can be after day care, at the breakfast table, at bathtime, before bedtime—or as often as you can when your baby's napping. Use these special times to shower your big boy or girl with love and affection.
Especially during the first weeks of your baby's life, try to get some help from others. A helping hand will not just lighten your own load, but also will make your older child's life more enjoyable.
A supportive partner can make an enormous difference during this transition from one child to two. Ask and expect your partner to help more with the kids.
Even though a father can't breastfeed, he can, of course, give the baby a bottle or two every day. Some babies do prefer to eat exclusively from the breast. But if the baby accepts a bottle of formula or expressed breast milk, it will allow Mommy more flexibility—and more chances to spend special time with the older child.
The "natural" division of labor is for the mother (especially one who breastfeeds) to care more for the newborn and the father to take care of the older child. But you need not fall into such rigid patterns. In fact, if Mommy handled the bulk of child care before the new baby arrived, your older child may resist spending so much time just with Daddy. Even if she welcomes Daddy's attention as a rare and special treat, however, your older child will miss a Mommy who suddenly shifts all of her energies to baby care.
So try to divide the labor more evenly. With the sole exception of breastfeeding, a father can handle every aspect of baby care that a mother can. So try to balance the time each of you spends with each of your children. When Mommy is feeding the baby, Daddy should of course entertain the older child. But when the baby isn't eating, Daddy is just as capable of taking care of the baby, giving the older child a chance to spend some time with Mommy.