Can anyone offer some advice on getting an 18-month-old to sleep at night?

Until now the three techniques we’ve had are 1) feeding to sleep on the boob, 2) walking to sleep in the sling and 3) falling asleep in the car. Number 3 is only good for naps in the daytime, number 2 is getting difficult as our kid is getting big and heavy (and is a PITA at night anyway, and number 1 is starting to become less reliable/effective.

What have you learnt about getting kids (particularly this age, if relevant) to sleep?

Many thanks!