Validation is one of the basic and most tedious tasks in application development. If there was ever a reason to use a framework this would be it. There are two ways that appear to be advocated by the CakePHP site and while both have benefits, I'm using a slightly different approach.

The "two ways" he mentions are auto-validation and using the validates() function (different from the suggestion in the CakePHP wiki of overriding the beforeSave() function). The first is built-in functionality, and is simpler to use. It allows you to define custom profiles for your values, ensuring they match the requirements. Using the validates() function is actually overriding a standard function and can be used to do more custom validation on the values passed back in.