I found some good info from the University of Michigan hospital here.
How can I take care of my child?
Some physicians feel that parents should not engage in any attempts at retraction, but this runs the risk of smegma collection and infection. In general, the foreskin requires minimal care. The following suggestions will help maintain good hygiene.
During the first year of life, clean only the outside of the foreskin. Don’t try to retract the foreskin. Don’t put any cotton swabs in the opening.
Gentle, partial retraction can begin when your son is 1 or 2 years old. It can be done once a week during bathing. Perform retraction by gently pulling the skin on the shaft of the penis downward toward the abdomen. This will make the foreskin open up, revealing the end of the glans.
During retraction, the exposed part of the glans should be cleansed with water. Wipe away any whitish material (smegma) that you find there. Smegma is simply the accumulation of dead skin cells that are normally shed from the glans and lining of the foreskin throughout life. Do not use soap or leave soapy water under the foreskin because this can cause irritation and swelling. After cleansing, always pull the foreskin forward to its normal position. (Note: A collection of smegma that is seen or felt through the foreskin, but which lies beyond the point to which the foreskin is retractable, should be left alone until normal separation exposes it.)
Avoid vigorous retraction because this can cause the foreskin to become stuck behind the head of the penis (this is called paraphimosis). Retraction is excessive if it causes any discomfort or crying.
By the time your son is 5 or 6 years old, teach him to retract his own foreskin and clean beneath it once a week during baths to prevent poor hygiene and infection. Gentle reminders are necessary in the early years.
In general, foreskin retraction is overdone in our society. Keep in mind that any degree of foreskin movement is normal as long as your boy has a normal urine stream. There should be no rush to achieve full retraction. Full retraction always occurs naturally by puberty. As the foreskin becomes retractable on its own, your son should cleanse beneath it to prevent infections.