Make questions open-ended.
If a child is drawing something that looks like a house, and an adult says, "Oh, what a nice house," that gives the child zero opportunity to share his creative train of thought, nor does it lead anywhere else. If you change the dialogue to "Tell me about your drawing," you've opened the floor for the child to discuss his process, and he might tell you that it's not a house at all, but something completely different.
We often — and usually unintentionally — steer our kids in a very specfic direction; for example, when we have them make Thanksgiving turkeys made out of a hand tracing (one of Christakis's least favorite projects). Those types of projects are cute and adults like them, but they don't allow our child to think creatively or originally.