Hi,
It really depends on your child, and when they are ready, you can softly encourage i.e sit in potty before getting in bath, or when you go to the toilet let her sit on the potty with you, or even if you know roughly when her constutional will be in the day sit her down on the potty and read stories to her this distracts attention from what she is actually doing!!!
Also i find that speach is a key factor if she can communicate well then you are half way there if she understands then you are definatley there!!!.
But got with your heart you know your child the best if you think she is showing signs then go with it and see if it doesn't work then stop! there are no rules, remember it will happen eventually! ( you don't see many adults wearing nappies).
Good luck