It is suggested that you first focus your study on one major topic at a time. For example, focus first on Securing Router Access and become familiar with the control to add to the router’s administration traffic such as AAA among many other topics. Then move your attention to securing users’ traffic with Access-lists and Zone-Based Firewall. Then move to learning cryptography and its application with IPsec. Familiarize yourself with the different types of IPS technologies, focusing on IOS IPS. Spend some times also reviewed Layer 2 security.
Do not neglect learning the theoretical portion of the material such as Security Policies, SAN Security and Voice Security, to name a few.
Practice your command line and SDM skills. You might wish to practice on gear such as a low-end Cisco 871, which can do zone-based firewalls. Cisco used to offer a Cisco SDM Demo, which you may be able to borrow from a colleague. You can also use emulators, use simulators, rent or borrow gear, but plan to practice the configurations and spend time understanding the show commands and spend a lot of time on SDM.
Learn each topic deeply. CCNA Security covers a broad but deep set of topics. To learn the topics to the required depth, read your primary study source and review the material. It's also helpful to use multiple study sources when possible, and practice the commands while immersing yourself in a topic.