Size and weight matter. Bear in mind that the heavier and bulkier the item, the more it will cost to ship. Pack your products with sufficient cushioning and protection but also keep them as light and small as possible.
Buy boxes and packing materials in bulk. If you are sending a lot of items, you can save a lot if you buy shipping boxes, tapes, bubble wrap and other packing materials in bulk. Most shipping supplies stores offer huge discounts when buying stuff in volume.
Avail of free shipping supplies. The USPS offer free shipping supplies. You can order them from the USPS website or you can ask for some in your local post offices. Alternatively, you can ask neighborhood stores for boxes and packing materials that they no longer need. You can usually have these stuff for free or for very minimal costs. Just make sure to re-use boxes that are still sturdy and can provide sufficient protection to your products.
Use Online shipping tools. Take advantage of eBay online tools like the Shipping Calculator to provide buyers idea on how much they will have to pay for shipping when they purchase your item. PayPal, USPS and courier companies also have similar online shipping calculators in their respective websites which you can use by simply providing the weight, and dimensions of your package. Other online tools let you print prepaid shipping labels and then arrange for pickup or drop-off of your packages, eliminating the need to fall in line in the post office or shipping companies.
Recycle. Reuse bubble wrap, packing peanuts, bubble bags, and shipping boxes if possible. Just keep in mind to use stuff that are still sturdy, clean and can still provide support, cushioning, and protection to your items.
Insure valuable shipments. Protect yourself against lost, stolen, or damaged product by buying insurance especially for high-value items.
Prepare international shipments properly. When sending items abroad, be sure you have all pertinent documents such as Customs Declaration. Also make sure that the item is not restricted or regulated in the country you are shipping to.