Read Richard Ferber's book "How to Solve your Child's Sleep Problem". It changed our life forever. CIO is NOT the Ferber method. You don't just drop your baby in the crib & walk away until they exhaust themselves. Ferber focuses on sleep association. Establish a routine that can be repeated every day, or even at both night time and nap time. Our routine at night is after dinner, our baby has a bath, then we have a bottle, brush teeth, read a book, and then she goes in her crib (awake), and falls asleep. Nap time is after lunch, we wash her hands & face, have a bottle, read a book, and then she goes in her crib (awake), and falls asleep. The idea is to get baby to associate that routine with going to sleep. And to get them to self soothe & fall asleep on their own.
Ferber will recommend sleep training. You let her cry for increasing intervals. In between the intervals, go in, pat her on the back, say "it's time for sleeping, I love you. I'll see you after naptime (or in the morning)". And LEAVE. So the first night, do 5 min, 10 min, 15 min, 20 min, 25 min, etc. intervals with the quick pat in between the intervals. Don't pick her up, and don't give her a bottle, etc.
2 months ago, we sleep trained our 1 year old. The first night, we did about an hour & a half of intervals. 5, 10, 15, 20, 25, and she fell asleep. The next night was 45 minutes, the next 15 mins, the next 2 mins. Now, if she cries at all, it's like 30 seconds. And from that very first night, she's slept from bedtime at 7:30 through the night until 6:45. BLISS!
I highly recommend this book. It's saved us with both of our kids!
Good luck!