We lucked out and got a baby that was an excellent sleeper from day one. That is until he began teething, and entered the separation anxiety phase.
One morning after very little sleep and at my wits end, I bought this book for my Kindle.
The No-Cry Sleep Solution: Gentle Ways to Help Your Baby Sleep Through the Night
It is a very good book, it makes you feel better just by reading it and there are very good suggestions for all situations. I found several good tips and techniques and noticed a difference right away. Bedtime and naptime were far less painful for all of us. The methods do take a while, but it is worth it for a happy baby and happy mom.