I'm having flashbacks. My oldest was terrible. Mostly because I trained her to need me and other comforts to sleep. She had to have a pacifier that I had to go find every hour upon the hour to put back in her mouth. She wanted to nursed even at that age every two to three hours and be rocked. It was a nightmare. For awhile I would lay on the floor and let her hold my finger through the slates of the crib so she would sleep and I would try to sleep.
It was awful. I finally just had to grow a spine and realize that my lack of sleep was making me a terrible mom and she wasn't getting enough rest either. So we started the method.
First night: I laid her down when she woke up...told her it was night-night time. I patted her bottom and sang her a short song and walked out. She cried for 15 minutes at the top of her lungs. I went back in (lights off) and repeated the above. I never picked her up or said anything except it was night-night time. I would shhh her or sing a soft, short song while patting her bottom.
It took about four or five repeats but she gave up and went to sleep.
The second night it only took about three times. The third night maybe the same or just two. The fourth and fifth night maybe just one or two times and the next week she was sleeping for six to eight hours straight. Maybe she would try to wake once during the night, but I wouldn't turn on the light, I didn't pick her up, I just checked her diaper, laid her down gently, told her it wasn't time to get up, patted her bottom a minute and walked out.
It worked for me. Good luck!!!
PS Made sure I didn't make that mistake with the second one. She went right in her crib as soon as she came home from the hospital. I never rocked her to sleep. She nursed, I sang and then I laid her down. She learned right off to go right to sleep and then if she woke up she would just go back to sleep on her own.