Use the template your client provides to complete your designs. If you have questions, don’t be afraid to reach out to your client or have them get you in touch with their printer directly.
If no template is available, contact your client to get as many specifications as possible, including packaging type (box, bottle, canister, etc.), dimensions and printing requirements. The more information you’re able to get, the fewer revisions you’ll have, and you’ll be able to deliver a better design.