Hoping to start a thread where we can get a few tips on how other people did this.
I can first share what worked for ds1 with us. At 4 months I started putting him in cot a couple of hours after last nap. And he just miraculously started to fall asleep at bedtime, after a while this also worked at nap time too. I just had to catch the right moment. If he cried I would sometimes rock him or whatever he needed then try again the next day. Over time he figured it out. When he learned to roll onto his tummy I had to keep turning him onto his back occasionally and sometimes I had to lean into cot and hold down his arms and sort of cuddle and shush him to hold him still. This seemed to calm him and stop him rolling over. He would fall asleep as I cuddled him.
My plan had been to do something similar with ds2 but he started rolling to his tummy at 2 months old, so my plans were scuppered! As soon as i put him down he flips onto his tummy. Then struggles and gets annoyed. I have tried my cuddling technique but it didn't work. He's now 6 months. I either feed or rock him to sleep, which is very easy. But I am wondering if I should try some gentle persuasion to fall asleep in cot. Just not sure where to start. Or maybe just worry about it later when rocking no longer works.
Sorry that's been a bit long. I hope my description of what worked with ds1 might help some others.