ebay local services

What is the best and cheapest way to ship something on Ebay?

I just started trying to sell some of my clothes on Ebay and have no idea what is the best and cheapest way to ship your orders. Most jeans and apparel are probably get into a large envelope or small box. In my auction I put that I ship to the U.S. Postal Service Parcel Post. I am not sure what the shipping and that I should pay more than is really just to make more profit or what? Can I buy boxes or wrapped in a shop or buy at the post office? I do not know what I'm doing. I suppose I should check with my local post office First:)

I found that FedEx Ground is the most reliable and least expensive to ship. They provide a tracking number and insurance for all their packages and rates are very reasonable compared to UPS

Using eBay Local for Automotive Listings – CIADA Tips of the Week – Denver, CO 80214