Scientific inquiry, or, as it's known to parents, curiosity, was the subject of a recent New York Times article, "Scientific Inquiry Among the Preschool Set."
To summarize, it seems that allowing children to play without adult interference might be the best thing one can do to develop scientific inquiry in a child. The work of childhood is play! Parents need to keep this in mind when scheduling activities for their children. Too much adult directed activity may actually inhibit learning.
To learn more about the importance of play, look for Einstein Never Used Flash Cards: How Our Children Really Learn--And Why They Need to Play More and Memorize Less by Kathy Hirsh-Pasek [305.231 HIR] or The Secret of Play: How to Raise Smart, Healthy, Caring Kids from Birth to Age 12 by Ann Pleshette Murphy [649.1 MUR].