Major developmental milestones to be observed in a 6 month old baby boy?

Develop milestones: Six month olds are generally sitting unsupported (briefly), holding a cup/bottle, rolling both directions, babbling including consonants, responding to emotions of others, passing objects from one hand to the other, searches briefly for objects, and brings objects to the mouth. They should be sleeping all night and napping at least twice daily.

Plays with you and: Can tell if someone is a stranger, will want to play with other people, show happiness, look at his or her image in a mirror, reach for things around him, transfer an object from one hand to another, make sounds, especially when others do, consonants first, roll over both ways, sit in a tripod fashion, briefly sitting without support, put things in his mouth, and support weight on legs when held up. See http://brightfutures.aap.org/pdfs/Visit%20Forms%20by%20Age%20110/6%20Month/A.Inf.PH.6month.pdf for advice at 6 months