It's a turnoff to the bidder to have to sift through all of your personal instructions. Make it short and concise. Try to notice if a bidder won more than 1 of your auctions. If they did, adjust the shipping charge accordingly. Be reasonable on shipping.
Most sellers charge more than is necessary for shipping.
Explore cheaper and effective shipping methods. Sellers use different ways to package the item, some are much better than others, and cheaper too. Email me if you'd like any ideas on this. It can be done effectively for 85 cents. Be sure to include information in your description, such as types of payment you accept, shipping charges, where you ship to, and the condition of the item.