Here is some great information on cradle cap, which is similar to “dandruff” in older children:

In infants with cradle cap, the scalp can have yellow scales and crusts, and might be greasy or dry. Often, the eyebrows are also affected.
Sometimes, it will cause the skin around the ears to get red, scaly, and maybe look a little greasy.
Cradle cap usually does not itch, and usually does not bother the baby.
The cause is unknown, and without treatment, cradle cap will usually resolve by the child’s 1st birthday.

Treatment:

Since cradle cap usually doesn’t bother the baby, try the oil treatment first. If it persists or worsens, then add the dandruff shampoo treatment.

Use baby oil or olive oil to soften the thick crusts. Rub it in with your finger, let the oil soak in for 15-30 minutes, then gently remove the crusts with a soft toothbrush. Wash the oil out immediately. This is very important, leaving the oil in too long can cause his whole face to break out in a rash.
Antidandruff shampoo. Use an over-the-counter brand, such as Neutrogena T-gel. Be careful to keep it out of her eyes. After lathering it into her hair, then massage the scalp with a washcloth. Use it once or twice a week for about two weeks.

When to see the doctor:

The scalp or skin starts to look infected.
The rash is spreading beyond the scalp.
The cradle cap is not starting to clear up after a few weeks of treatment.