You might find these PCI related white papers useful in helping you understand the requirements for PCI DSS compliance:
1. PCI DSS made easy
Addressing the Payment Card Industry (PCI) Data Security Standard
2. Automating vulnerability management for PCI DSS compliance
A practical approach to network security and PCI DSS compliance
3. Automated event log management for PCI DSS compliance
A practical approach to effective network security
All three white papers are free, no registration require to access them!