Routine.
We had a routine from when DD1 was 2 months old and it has never changed. Both DDs (16mo and 3.9) are in bed by 7.15 and usually asleep by 7.30. Our routine is:
6pm: TV (if it has been on) goes off, and we have quiet, wind down time in the lounge, with books or a gentle game.
6.15: I start running the bath.
6.20: DDs in bath, do teeth etc.
6.35ish: Out bath and upstairs to get dried / ready for bed.
In bedroom (they share) DD1 gets her PJs on, does her inhaler, chooses book and teddy whilst I get DD2 ready.
We then all sit on floor and I read to DD1 / she reads to me whilst I BF DD2.
When story is finished DD1 gets into bed and I sing her a song.
I then get read DD2 a little book, we turn on some relaxing music, kiss DD1 goodnight and turn out the light.
I put DD2 into her cot (or BF her to sleep occasionally) and pat her until she's in a deep sleep. Usually DD1 will fall asleep before I leave, if not we have an extra kiss and cuddle then I leave the room.:4