We started reading and signing to B around 4 months with basic words (milk, eat, drink, sleep, bathe, book, car, plane, etc.), black/white picture and touch books with simple words, rhymes and numbers. Lately, he likes colourful peek-a-boo books with foldable, pull out tabs/toys and books with real baby photos and different textures. He still loves nursery rhymes and songs that we make up/"bastard"ize and use every day. Evidently children use familiar words and rhymes in their speaking vocabulary at a more rapid pace as well as contexts and concepts such as counting, time, measurement, position, and weather. B reaches out to pick/grab books when he sees them, and seems to engage and focus quite well when we read to him. Since he can't talk, sing or sign back yet, I take this to mean that he understands more by now....! He does babble a lot at times and experiments with his tongue for pitches and inflections to indicate that he's curious, wants yes/no, sleepy/tired, bored, happy, satisfied, etc.
Meanwhile, B now has 6 teeth! That's a record among his peers who have on average 2 teeth. He got the 2 lower central incisors at 6 months and then the 4 upper incisors (central and lateral) over the past few weeks. Ouch! While the teething resulted in plenty of sleepless nights, seeing his pearly whites makes all those groggy pats/cuddles/rocking worth it. I hope there'll be a brief respite so that he can eventually settle back to sleep "through the night" again (i.e. sleep by 8p, may wake briefly 1-2x but settles back on his own, real waking at 6/7a to start the day). Also, he seems to put everything in his mouth these days -- that is, everything BUT his actual teethers. What irony.
Physically, he's pushing up to stand wherever he can -- cot, sofa, toystool, etc. though he tends to tiptoe still. He continues to creep, roll, turn, scoot backwards, rock and bounce as he tries to move more than 2 steps forward. We've installed our window grills and bought a play "fence" - waiting for him to crawl for real! Guess B's been too busy growing teeth to focus on his crawling this past few weeks :)
Read more:
http://www.parenting.com/article/best-books-for-every-baby-stage
http://www.rwitap.com
http://www.babycenter.com/0_developmental-milestone-talking_6573.bc?
http://www.babycenter.com/0_your-childs-teething-and-tooth-loss-timeline_10356447.bc?
http://www.teethingtips.com/teething-symptoms-and-why-it-hurts/