It's easier as they get more verbal, but you can just talk about the day until then. We've always done it while putting on Tyler's pajamas or while sitting in the chair snuggling before bedtime. If you aren't home with your LO during the day, you can pretty much use whatever you know they did during the day. You'd just kind of babble on, like "So what did you do today? Oh, that's right, X came over to stay with you. What did you have for breakfast? Cereal? Mmmm. Did you play with trains today? I bet that was fun. Did you go anywhere in the car? You went to the store? Did you see apples, and bananas, and lots of people? Etc etc" As they get more verbal, you can ask questions they can answer, KWIM?