what really worked for me is the curtains!
during the day when my babies have naps i leave the curtains open so that they know it is daytime.
at night i make sure there room is nice and dark....and if i needed to feed them or anythin i did it in the dark without moving them too much. my kids were bottle fed so i would change them and feed them without takin them out of bed.
then when they woke up anytime after 6am i would open the curtains up and blind them with the sun so they new it was day! i would make so much noise and grab them out of their cots straight away.
i think its really important for kids to know the difference between night and day. my little boy is 3 now and when he sees that the sun has gone down he tells me its time for him to go to bed. and sure enough he is still up at the crack of dawn with the sun!
good luck