We're 4wks and this is how we 'programmed' DS:
TV on in the background all day, blinds open, lots of chatting to him all day (absolute b**cks mostly!), lots of eye contact during feeds
Darkness & silence from approx 8pm to 8am, no eye contact or chatter, no nappy changes unless really needed
Bedtime routine - 7pm ish bath, massage with Earth Friendly Baby Chamomile lotion (the smell makes ME sleepy now, by association!), into bodysuit & grobag, given a feed in our bedroom in total darkness & silence & then put downstairs in the moses basket to sit with Daddy until he comes up to bed at 11pm (my nap opportunity for a few hours!)
In the morning I brightly say 'good morning' and chat to him while I change his nappy & outfit, then we go downstairs for a feed in front of BBC Breakfast.
This method has worked from about a week old, at night he tends to feed at 7.30 ish, 11ish, then usually only 1-2 times in the early hours. Not exactly 'sleeping through', but lets me snatch a few little naps each night & his weight is gaining nicely!