Behavior. Most children are not ready to begin potty training until 2 years of age. When she tells you that she has urinated or had a bm in her diaper, you can start to offer her the use of the potty.
When Ready. I believe that when a child wants to be changed when wet 80-90% of the time, they can be potty trained! This means that they do not wet their diapers or pants and will do anything to stay dry.