This is intertwined with timeliness, but deserves its own category.
I have streamlined my product packaging process and mailing protocol to the point that each package can be assembled in less than 5 minutes (from gift wrap to stamped bubble mailer) and mailed out the following business day.
As a customer, once I make my payment, I expect that the product will arrive in a timely manner.
As a seller, I learned that the greatest roadblock to getting the product to my customer can be the packaging process.
Put everything you need in one location so that you don’t end up forgetting about the order when you are hunting for packing tape – and then get distracted by the many other elements of your life.