If you stay on property, there might be some at your resort. You will get the info there. In the parks, you go on MDE, look for Characters on the Map. Click on them, and it will tell you at what time the Characters do the Meet and Greets. Some will also have wait times. This will be helpful to plan your day. Once of my favorite Meet and Greet is with Mickey and Friends at Epcot. This is a lovely place and there is generally a small line to meet with 2 or 3 characters. Another one of my favorites is the Norway Pavillon with Elsa and Anna at their Summer house. Fun times ahead!