When you work as a postal service window clerk, one of your biggest responsibilities is being the face of the United States Postal Service for customers in your area. You serve customers by selling stamps, pricing packages and preparing them for pickup, accepting letters and distributing post office box mail, and accepting payment for other postal services provided by your branch. Your duties mean you need a working knowledge of prices and products used to ship items. Additionally, you need financial literacy skills to count change to give to customers and perform drawer audits. Other beneficial skills include excellent customer service skills, attention to detail, and the ability to learn and follow protocol.