Great question--and one that has been on my mind too! My girl is 16 months and is so interested in the bathroom. So, last weekend we bought her a little potty and the first day she went poop in it! Since then, she has gone pee in it twice more! For the first couple of days, she wanted to try sitting on it every 30-45 minutes! So, I let her run around the house in just a diaper and when she went knocking on the bathroom door I take off the diaper and let her sit on it.
She's vocal but doesn't say many words right now, and I don't think she quite gets the idea of being "wet" or "dirty" although she does know what her diaper is and where to go when we change it. So, my though is that the potty is a good idea, but I'm not going to push her to use it. I'll just let her sit on on whenever she wants and take her in there with me whenever I go. And, if I happen to catch her making the "poop face," I'll take her in there.
Good luck--I'm going to keep an eye on your answers for other ideas that I can use!