How can I move data from my old phone to my new phone?

Episode 1408
Cathy fromCathy has an old Samsung Android phone and she's ready to upgrade. She wants to know if getting a previous model from eBay a good idea. Leo says that she can get a good deal on one, but chances are it won't be updated. So she'd have to have it updated. Leo advises going to XDA Developers to learn how to root the phone to put a new version of Android on it.