Use the real materials
Test with the same bag material and products you plan to pack. The way a light snack bag gathers may differ from a larger bread bag.
Repeat the process
Have more than one worker try the closure if a team will use it. Look for consistent feeding, easy handling and a tidy finish. Record observations instead of relying on one good example.
Ask the right commercial questions
Confirm sample availability, any delivery conditions, current carton price, dispenser compatibility and the lead time for the actual order. The sales team can confirm these terms before you commit.