Prerequisites for Data Science
I would say that trying out the resources online such as the Explore Data Science course and Andrew Ng's ML Course on Coursera (mentioned in the notes above) are great. However, nothing beats true data that you understand inside and out. After picking up some skills from Explore Data Science, I propose you collect your fuel usage data continuously. Collect the basics: city, state, gallons, total cost, and your vehicles mileage. When you forget to enter it, then you have to learn how to work with missing data. As you feel more comfortable, enter in kaggle contests. The data science community is growing so quickly that the online resources are vast and will help you identify any areas where a text book is what you need. Good Luck!! Have fun!