One thing that really helped prepare my son was watching us go on the potty. It sounds kind of gross, but he learned many things from observation and explanation: that pee and poop come out your bottom, that big kids don't use diapers, you need to pull down your pants, mommy sits to pee and poop, daddy can stand to pee (not relevant for a girl) but can sit too, daddy sits to poop, how we wipe and flush, then wash hands, etc. It wasn't that he was gawking at our private parts, but it was a lesson in how boys and girls are different.
The bottom line is that we did not pressure him to learn to use the potty, we presented it as a part of life. We let him watch us, ask questions, look in the potty. Every now and then we would ask him if he wanted to sit on the big kid potty. In turn, it wasn't a scary, new thing. He just did it. Kind of like eating with a spoon or fork, you just do it. It takes practice, but they learn!
We also put a little potty out for him to become familiar with, but he didn't use it much. He liked to pretend to go in it. He was in day care at the time and they took the toddler kids to the potty very regularly. Some of the older toddlers were already trained. One day his teacher told me he had been in underwear all day with no accidents! I went to Target and bought tons of undies and he had very few accidents after that! Talk about positive peer influence!!