If you have absolutely no idea how to grade coins, you have no business buying coins without help. If you do not know how to grade coins for yourself, you will eventually learn, and it could very well be an expensive lesson. When selling coins, you don't have as much of a problem. Simply take the coins to a couple of different dealers and get their opinions as to the grade. Always ask for the grade opinion before asking for a price as it can help in negotiating a fair price.