Try Solve Your Child's Sleep Problems by Richard Ferber. It was really helpful at our house.
The "cry it out" method is NOT just leaving them to cry. Put your son down awake. He'll cry. Visit after 3 minutes, so he knows you're still in the house, and aware that he's upset. After you leave, he'll cry again. Visit after 5 minutes. When you leave again, he'll cry again. Visit after 7 minutes. So on and so on. I max it out at 7 minutes; I don't go in at 9, but do 7 again and again.
This has the benefit of teaching your child to soothe himself to sleep. When he wakes in the night, repeat the process. He'll learn that when he wakes at night, he can put himself back to sleep.
Also, keep a consistent bedtime routine, to sort of signal his body that it's time to sleep.
It'll take about 3 days. Hang in there, mom.