On the Debuggable blog Felix has posted two quick tips you can use in your CakePHP application - one related to debugging and the other about custom config files.
For tip #1
If you just put a debug() statement in, you will see hundreds of outputs and would not know which one belongs to the case you are interested in. My favorite solution to this problem is to use the Configure class as a toggle for showing the debug information.
For tip #2
This is a very simple one. To make your application configurable via a global config file, all you need to do is the following.
Both come complete with code examples.