I would start by familiarising myself with the 10 domains of the CISSP, then look in-depth at the bits you think you're going to need to know about:
Access Control
Categories and Controls
Control Threats and countermeasures
Application Development Security
Software Based Controls
Software Development Lifecycle and Principles
Business Continuity and Disaster Recovery Planning
Response and Recovery Plans
Restoration Activities
Cryptography
Basic Concepts and Algorithms
Signatures and Certification
Cryptanalysis
Information Security Governance and Risk Management
Policies, Standards, Guidelines and Procedures
Risk Management Tools and Practices
Planning and Organization
Legal, Regulations, Investigations and Compliance
Major Legal Systems
Common and Civil Law
Regulations, Laws and Information Security
Operations Security
Media, Backups and Change Control Management
Controls Categories
Physical (Environmental) Security
Layered Physical Defense and Entry Points
Site Location Principles
Security Architecture and Design
Principles and Benefits
Trusted Systems and Computing Base
System and Enterprise Architecture
Telecommunications and Network Security
Network Security Concepts and Risks
Business Goals and Network Security