We practice Elimination Communication. It seems odd to call it that with Sasha anymore, since she has been out of diapers for about a year. She literally tells us when she needs to potty, so there are no "signs" for which we must watch. We're also doing Elimination Communication with Spencer.
A lot can effect babies and toddlers as far as communicating their needs, including elimination needs. When we moved in October, Sasha was suddenly making puddles everywhere. We knew she was capable of getting to her potty or telling us she needed to go, but we had miss after miss after miss.