That is a tough one as we all loose sleep, a casualty of parenthood. What you don't want is a pattern. That is what needs to break.
For us, we have 3 kids, 5,3 and 2. Two boys and 1 girl. If they get up, we go to thier bed. Comfort them, then put them down and leave (lights off, night light on). They may get up again but if you keep doing the same thing (comfort then leave staying no more then 5 min or so. They get tired, know you will be leaving and start breaking the habit on thier own. In the end it is the comfort they crave, and one on one time with you. But they have to learn that bedtime is bedtime not Mommy or Daddy time.
Sometimes crying will happen, but it won't hurt them or scare them mentally. Lack of sleep however hurts everyone. Especailly if you have a busy day to day schedule.
Sometimes enticing them with special one on one days or going over the next days events gets them psyched to go to sleep so they can do the fun stuff the next day.
Also, not sure if you are artsy but we paited murals in each of our kids rooms so they love thier room. Each room is different so they have thier own "space".
Good luck, lack of sleep is one of the hardest things!