We started a bedtime routine with DD when she was between 3 and 4 months old... Around that time she seemed to start getting tired at around the same time each evening. She's now about 6 months old, and the routine seems to work well for her. She usually starts to get a little fussy between 6 and 7. As soon as she does, we take her up for a bath (mostly because she LOVES the bath). We then get her dressed, read some books (as many as she's interested in), and then I nurse her in our bed until she falls asleep. If she doesn't fall asleep nursing (and this is really rare), we either read some more or walk with her and sing to her, depending on how tired she seems. We have a video baby monitor, so I can watch her sleep (and see if it looks like she's going to stir to nurse).