Self soothe... When'to start??

Angela • My name is Angela. I am pregnant with my first little bundle of awesomeness!! I'm so blessed!
Hi ladies, I have a 6 week baby girl. I am fixing to go back to work. I am a preschool teacher and my sweet girl will be going to the nursery when I get back. I want to know when is the best time to start getting her to self soothe.? I know in the nursery she will have to be able to self sooth. I'm not sure how to start her to do that. I am a rocking to sleep mom or she'll fall asleep after eating. 
Any advice on how any one got their baby to  sleep on their own would be great. Really hoping to avoid the cry it out method. 😊