This is what i found the hardest - teaching your little ones day from night, coz simply they just do not know. Like other girls have said, not making the room totally dark during the day, not necessarily creeping around the house careful not to make too much noise during the day...i would find if mine slept longer than 3-4hrs (which was rare in the day) i would wake them....You have to look at their sleep period over a 24 hr period - and if they're getting the bulk of their sleep in the day...of course they're not going to sleep at night. But in saying that, she is only 3 weeks old, this whole universe thing is new to her....i found around the 6 wk mark we kinda got into a routine- ish !!!

Good luck !!