probably not what you want to hear, but let him cry. my pediatrician suggested 5 minutes the first time, 10 the second, 15 the third. we never got beyond 10. And, yes, it was incredibly hard not to go comfort him. I'd look at the clock when I first woke up and then willed myself to stay put - no noise, light, etc that he could see or hear through the hallway. If there was still crying, then, go and say "its night, night," rub his back a little and go back to bed. its rough to do, but he will learn to put himself back to sleep at night and its one of the best life lessons you can ever give him. Also, make sure his tummy is totally full at bedtime (we did bedtime oatmeal at that age).