It is always important to look your best...SMILE!! Also, let them know what YOU CAN DO FOR THEM. Employers want to know what you can do to help them succeed. "I am a people person and I feel that it is important to meet the customer's needs. I feel confident that I can do that."(even if you don't). "I feel that with these skills I can be a great asset to your company. I have experience handling customer complaints and can deal politely and effectively with your customers."
GOOD LUCK!!