On your lighter "fluffy" items (Clothing, stuffed toys) whenever you can get away with it, package first in a zip-lock bag you can purchase cheap at any dollar store and squeeze out the extra air and zip. Then package in the smallest box you can get away with. And remember some crazy folks open their package with a the sharpest knife they own. Add a piece of cardboard the top and bottom along the opening. Postage is based on weight and/or actual size of the box, mailing services and the distance its going. Anything you can do to reduce the size of your package will reduce your postage. Ask your friendly dollar store to save an assortment of boxes for you. Most won't mind. The more of a variety you have on hand the easier it is to pack your items and mail them for the lowest cost and still be able to package them for safe arrival. If you need to re-enforce a box to protect your more delicate items add a bit of thick cardboard around your item(or box inside a box with cushion between). It won't add much to your final shipping price. Remember, your packages may be going many miles with lots of handling and you'll have an upset customer if it arrives damaged. And lastly, when you're creating your listing accurately measure your packaged item and enter in the info. Always safest to round up to the next cm on each side and add a few grams to your package weight. The system will tell you if your package is too heavy or too small for a particular service. I myself base my choices of services to offer on the value of the item. Up to your own personal judgement.
-CM
PS. For anyone interested in reducing their shipping charges
