Customer Comments/Instructions

[tiggerific]

Is there an easy way to add a "Customer Instructions" field to the end of the ordering process?

Ideally, I'd like to be able to add custom fields to either items or to orders, but for now, a single field that lets the customer enter instructions, comments, other requirements, etc. would work for the most part.

In the past I've had to customize drastically to add custom fields to items, such as add fields to the database and modify all the templates and coding, etc.