Personally, I pretty much GIVE coins away to Little Kids... even at the Coin Shop. If you were to take coins to a coin shop, here's what WE pay: Common Wheat Pennies: $0.02 / EA (we sell them for $0.04) Common Indian Head Pennies: $0.50 / EA Common Buffalo/V-Nickels: $0.35 / EA (only with readable dates - otherwise Face Value, as we give them as change) War Nickels: $0.40 / EA Common Silver Dimes, Quarters, Halves, Dollars (Unless Valuable Dates) - 8 X Face Value Non-Silver Foreign Coins: $5.00 / LB Anything else New/Clad/Nickel is just Face Value. We DON'T buy newer date ERROR COINS, $2 Bills for more than Face, or any paper money that is not Crisp Uncirculated, generally, unless Older. SO... now you know that you don't get too much by selling them to Coin Shops that have to Re-Sell them!
The way I figure it, fifty wheaties sold to you would still give me another dollar to spend at your shop. And I have more than fifty of them!
I have found a many of good coins at yard sale. Mainly from folks not knowing exactly what they had. Usually thrown into a change jars with a price tag of 5 cents each as I start to pull out Indian head pennies or war nickels. As to get what the coin is worth, put anything worth some value in a 2x2 and set them were someone can keep an eye on them. I have seen some people pull some fast ones at yard sales when the owners get busy. Remember also people are expecting to pay yard sale prices at a yard sale. If you have some higher end coins it may not be the place to sell them.