When you approach product packaging, where do you start?
If you have a brand concept statement or a value proposition, you can begin there. These statements define, among other things, what's unique about your product, including benefits and features. Knowing and articulating this is the foundation for all copy - packaging no less.
If you're not there yet, and if you're pressed to come up with packaging fast, you can do what I did for Heavenly Sleep Liquid Melatonin.