I usually wait until they were a little older (8-10 months) before starting sleep training, and at that point it usually goes very quickly. I do let them cry it out, but I go into the room every few minutes to calm them down. The first night, it will be every 5 minutes or so, next night every 10 minutes, etc. etc. When I go in, I lay them down, pat their back, talk to them, but DO NOT TAKE THEM OUT OF THE CRIB. We just did it with baby #8 and it took all of 3 nights before he finally started falling asleep on his own with minimal to no crying.
