We used to rock our now 9 week old to sleep every time. When he was in a deep sleep we would put him down and he would sleep anywhere from 30 mins to 4 hours. At 6 weeks I decided to stop this and put him in his cot. Obviously he cried and sometimes we would need to go in and out 6 times, but after a few days he got the hang of it and now goes to bed mostly by himself in his big cot. It was worth the effort. You get good days and bad days at the start, but 3 weeks on, the bad days are minimal. He still wakes lots after one sleep cycle, and he is really hard to resettle, but I was told that if he only has another 5 mins sleep, that is still considered successful as he has resettled.This will eventually lead to him learning to resettle himself. Persistence is the key. I tried to put him to bed without rocking him earlier, but he wasn't ready. I think at 6 weeks he was finally ready. We keep DS up about 1.5 hours max, sometimes he is tired before this, but I make sure he is ready for bed and this is the key. Good luck