I agree with dottie, train them early, as soon as they show signs of readiness.

The first thing I would do is get a good potty training book and a peeing doll. Go over the material with her and tell her she is a big girl and is now done with diapers. At first take her every 15 to 20 minutes so you can catch her being succsesful. When she goes in the potty make a big deal about it. When she has a accident do not do anything. Do not react at all, just clean her up and change her clothes. Gradually increase the time between potty trips as she stays dry. Have any other care givers follow the same pattern you are doing at home.

Another thing that worked really well when my daughter was capable of staying dry was I quit taking a diaper bag out with us. If she had an accident we just went home(she was not in trouble thats just where her clothes were). This worked for her because she loves to be out and about. If our DD had to leave a play group or the park because she was wet it really motivated her to make it to the potty next time. Just make sure the places you go have potties and your DD knows where they are.