The OP is written primarily for social scientists, and primarily those pursuing an academic career, but many of the points apply to doing work with any kind of data, including sports data, especially:
1. Learn to code in some language. Any language.
2. Stop using Excel. Or at least stop ONLY using Excel.
3. Learn about how to properly care for your data.
4. Write a data management plan.
5. Read Reinventing Discovery by Michael Nielsen.
6. Learn version control.
8. Let everyone watch.
These echo closely the core values of Chadwick Bureau, and how we go about producing and maintaining quality datasets. We hope to come back to some of these points in products and projects we have planned for 2015, so do stay tuned.