My DD is 7 wks, and I just got done doing the same thing, so I can tell you what's worked for us. First, I waited until she was spending more time awake, content and alert on her own during the day. First it was just minutes, then 20 mins of crib time while I got dressed, etc. that she was ok being apart. To me, this was the signal that she was detaching on her own and transitioning from that super-fragile neonate stage to an awareness that she is her own person, and doesn't need me every moment.
I turn the lights way down for at least an hour before I want her to sleep. I change her in dimmed light and nurse her in dimmed light. (We use a dimmer and a cheap taplight from Target.)
Then, after DD is swaddled and asleep in my arms from nursing followed by bouncing or rocking her, I keep bouncing or rocking her for about 5 minutes to get her into deeper sleep. She usually starts dream-nursing at that point, and I know she's gone under. Then I slowly stop until I am holding her still, and move the way I am holding her so I can put her down as gently as possible.
I then put her down in the bassinet slooooowly with my hands still under her. Then I gently slide my hands out from under her. Usually we do this once with her waking up mid-way, but then get it right the second time and she sleeps well.
At first, she'd only do this for one sleep, and then have a hard time going down apart from us again, but around 6 weeks it started working after the first night-nursing, as long as I let her get into deeper sleep in my arms and then didn't startle her awake.
I sleep so much better now. Good luck!