I don't have anything terribly innovative, but fwiw here's what I remember from seeing our two pass into the stage of sleeping all night...
- Establishing a set routine helped. We didn't don't put them to bed at 7pm one night and 11pm the next night and 8 pm the next and so forth. We also made sure feedings and playing and such were at specific times, and gave them a wind-down period before bed when we would just sit with them quietly or read a story.
- We kept classical music playing in their room while they slept, not sure if that helped or not.
- Whether we responded to their cries varied. Sometimes the cry indicated that something was just wrong. However, if they were dry, fed, etc., and it was just a plain normal cry then we let them cry themselves to sleep. We felt that if they learnt that crying would always get attention then they'd end up crying every night and it'd be a constant struggle. We also did this because we didn't want them sleeping with us, but in their own room.
- Not sure if baths helped, but it might have. A play period about a half hour to an hour or more before bed might have helped tire them out, not sure if it did but we tried (at least with our second one).
- As they got older we created situations in which they'd have choices (or just gave them the power to choose), first so that they could get used to making choices, and second so that they would feel like they had some power over their nighttime routine. Choices could range from whether they wanted to read book X or Y, whether they wanted to get baths on "evens" or "odds" (days of the week), whether they wanted to play in their room or in mommy and daddy's room, etc.
Thankfully both our babies were very good and transitioned easily, and rarely gave us problems, at least with regard to crying. Now bodily fluids... ugh...