Your point-of-sale system is a goldmine. Look at the last 12 months of sales by product category. Which devices and flavors sell through fastest? What's the average monthly volume? That's your baseline.

If you're new and don't have a year of data, use what you have—even three months helps. Combine that with foot traffic patterns. If you're in a college town, you'll see seasonal spikes. If you're near a military base, demand might correlate with paydays.

Don't forget to factor in repeat customers. A shop with a loyal base can sustain a different product mix than one chasing tourist traffic. Your own data beats any industry report for predicting your next month.