If you are developping an application, we strongly recommend that you use one of the debug builds during development. Debug builds are slightly larger but contain the information necessary to identify which lines of code may be causing problems - this is important when reporting bugs or finding workarounds by looking at the source.
Many core classes have debug disabled by default.
The distribution comes with a number of properties files, most of them contain some obvious debug settings in the form:
debug=false
someOtherSetting=someValue
In all cases, what you need to do should be pretty obvious...