If you’re doing extensive debugging and introspection with your web APIs (or perhaps debugging Web Views), here’s how to configure Charles to proxy SSL connections from the Simulator and on-device:
SSL connections from within iPhone applications • Charles Web Debugging Proxy
As of Charles v3.9.3 there is an item in the Help menu, “Install Charles CA SSL Certificate in iOS Simulators”, which will automatically install Charles’s SSL CA certificate in your iOS Simulators.