No, I never ever left him to cry, it makes me cry!
At about 6-7 months I made a pod for him on the bed out of my maternity body pillow under the duvet (like a sleepyhead) and lay down next to him while he slept because he liked me touching him. Gradually I managed to put him down and just lay next to him without touching. Then I made up the pod in the cot and lay him in it and made sure I was still touching so he would be calm. Eventually I was able to just lay on the bed next to the cot. Final step was leaving the room!
It took maybe 1-2 months but we managed it without crying and it had the beneficial effect of making it easier to put him down for nighttime. He was waking every 45 min at one point, that nearly killed us.
For timings I just looked up how long a baby of that age should be awake for. When he woke I'd check the time and start a timer to tell me when he was supposed to have been awake long enough and then start trying to put him down for a nap.
He's a brilliant sleeper now, 2-3 hour nap after lunch where I literally go into his room, turn on the white noise, give him a kiss and put him into his cot. He immediately rolls over and goes to sleep!
At night he has a bedtime routine which DH does at 7ish, I think it's stories, songs and then cuddle before going into the cot. He then remains asleep until 7ish.
I think he's a good sleeper because he knows that we would be there if he got upset so he can relax enough to sleep instead of getting stressed by being left to cry. On the occasion that he does wake up, he can be settled within 5 minutes without taking him out of the cot.