I don't leave DS to cry - he's 9 months and sometimes does some random shouty bits, not crying - if he starts sobbing, he gets stroked, patted or picked up.
He's very good at going to bed, partly because we established a good bedtime routine early on (bath, story (of the 'that's not my...' variety!), feed then bed) and he also has an ugly bear light show (the VTECH one from Mothercare) which plays quiet music, nature sounds and projects a light onto the ceiling.
He now thrashes about and gets cross if I don't put him in his cot when he's tired.
But, and this is a big but, this also works well because DS is a very good baby. I don't follow a strict routine with him food and sleepwise - he has three meals a day, some breastmilk in the morning, at night and once or twice during the day and he drinks quite a lot of water from whichever cup is clean(!) - a miracle in itself when I think how hard it was to get him to take a bottle for when I went back to work!
I am extremely lucky and I don't want you all to hate me for having a baby who sleeps, eats and smiles, so if I tell you that when AF pays a visit to my poor endometriosis-riddled body, it's like labour itself, will that help? It's true, btw