As many mothers have said, I think a routine is important. Give her a bath, read her a story, rock her, whatever works for you all, at the same time/same order every night (after the routine is established, you can vary it sometimes as needed). Then, as most others have said, you have establish a routine of actually going to sleep. I personally am not a proponent of the CIA (cry-it-out) method; however, I did a modified version of it with my youngest (now almost 2yrs) and it worked really well. I did the pre-bed routine with her, then put her in the bed, patted her, told her I loved her & left. She cried of course, and after 5 minutes, I went back in, rubbed her back, patted her butt, but didn't pick her up. I stayed 1-2 min max, then left again. She cried again & I waited 10 min this time, then went in & did the same things, reassuring her but never picking her up. I left again, she cried, I waited 15 min, same thing. The longest she ever cried with this method was 30 minutes straight; she was going to sleep on her own after the 10 min increment after just a couple days. Now she sleeps all night (most nights, lol).
But remember every baby is different. Some will take to it easily & some will be more stubborn. But I think most eventually come around to it. I personally think allowing a baby to cry for more than one straight hour is too much, but it's all personal preference. You know your baby's personality better than any of us or any parenting book.
One thing to note, don't start a new routine when your baby is sick or your family/lifestyle is experiencing a lot of change. Since it may take a week or more to establish the new pattern, you need to make sure you start it when you know you can be at home & do the same thing every night for at least 2 weeks. Again, every baby & situation is different; this is just a guideline compiled from parenting books, friends, & personal experience.
Good luck!!
A.