I had trouble getting my daughter to sleep so I would make a big thing out of her putting her baby to sleep first and then would do everything she did to her doll, to her...something she noticed and made use of. She would do a few little things to her baby as a way to let me know she wanted extra attention or something. We had lots of fun doing this..

I do this also - in fact my kids almost insist on it!  I started out following a eat-play-sleep cycle (where you feed them when they wake, give them some awake time, which turns into play time as they get older, then put them down to sleep), which I believe helped them to sleep through the night from quite an early age.  My eldest first slept through the night at 4 weeks (for about 8 hours) then by about 2 and a half months was doing it everynight.  My youngest took till 3months to sleep through the night, but has done it pretty consistently since.

i have done a similar routine with miss3.9 since she was born, and it's worked for me also.