If you are purchasing cheap items on Amazon and flipping them on eBay, it is a great practice to include a note and make sure you send the item as a gift. On the Note you should write something like:
You will notice that your goods have arrived in an Amazon box. Like many sellers I use Amazon as a fulfillment house. I also spend many hours finding my customers the best deals. If you are interested in hearing about my other deals feel free to contact me. Thanks!
Other things to remember when flipping on Amazon and eBay is to check the eBay cost calculator. I use an app on my iPhone or visit the site: http://ecal.altervista.org/en/home.php
Flipping items on eBay from Amazon can be very profitable as it requires no inventory or overhead. All you have to do is find products that are cheaper on Amazon than they are on eBay. Make sure that it is a product people will buy and be sure to use the cost calculator to make sure you are making money.
I will update this post with more flipping tips as I encounter them. Thanks!