I've been going through a number of textbooks, building sample apps, so I know my environment works. I downloaded the AVCam sample code from Apple. It says:
AVCam was built with Xcode 3.2.5 on Mac OS X 10.6.6 with the iOS 4.2 SDK. To build the app, simply open the project and choose Build from the Build menu. This project cannot be built for the iOS simulator.
When I follow these simple instructions, I get 79 errors and 120 warnings, and no app. There must be something basic going on here.