the only thing I did was make it super dark at night and no talking then just feed and change and back to sleep, and also let them stay up and play with them in the day especially in the hours leading up to bed...mine are 5 weeks and only wake up 1x at night and go straight back to sleep after.
Play with them during the day, try to break up the long naps, go on short walks, keep it as light as possible during the day and dark at night, have a bedtime routine. That all worked for me, my son sleeps from between 9-10 until about 5. @mandaskye