The folks over at The Daily Green have a great article called Lead Poisoning Prevention Tips in which they discuss ways for parents to protect their children from being overexposed to lead via lead paint on toys, lead used in metal jewelry, and other sources.
The article goes into more depth, but just as a preview:
1. Check the Toys
2. Remove the Source of Lead
3. Consider Other Sources
4. Maintain Older Homes
5. Check Your Child’s Blood Lead Levels
6. Ensure Good Nutrition