This post offers a wealth of information when it comes to recording things like webinars, Google Hangouts, and Skype calls.
Before we dive in, I want to highlight two takeaways:
1. If you have Windows XP, you may not be able to do this without a workaround/hack (more detail in the PDF).
2. The TechSmith products that work best for this task are Snagit 11.1 on Windows, Camtasia for Mac 2.2, Camtasia Studio 7 or 8, and Camtasia Relay 4.1.1.