Take the time to do a quick peek. It only takes a second or two. This will come to the average rookie after they have done just what you, I and many others have done for years, when looking for or actually finding the older coins. I have found, that even when the pennies are extremely caked, a quick pinch of the "oreo cookie" they sometimes fall out of, the Lincoln head will usually be visible first and when you cannot distinguish the Lincoln Memorial on the other side, more often than not you have found a wheatie. (the exception to that, where I live, is when you are digging just after it has rained or is muddy/water soaked). Like Beale said, keep the silver separate and protected from the other coins and junk in your pouch. The silver will most likely be obvious when you find it, because it usually retains some of it's luster (depending on combination of water/soil conditions you find it in) and tend to be worth about ten times their face value compared to the wheat pennies. DON"T RUB the silver coins! No genie will pop out of them, and you might be sorry you damaged a "key date' coin.
I find wheats everywhere. On the modern playgrounds, at the older houses, even in change from the gas station, etc. There are still plenty of them in circulation. I am still holding out for that 1943 copper wheat!!!!! I think that when you keep track of where you find an older coin, there may be others. Possibly the fill dirt in the baseball field came from an older housing area, and there may be other older coins in the area. Or perhaps a child had a penny in his/her pocket and didn't realize what they had when they were playing on the swings and as such, is probably the only wheat (or any other older coin besides modern clad) that you might find. But I have found it to be a good idea to keep track of both the "condition" of the coin, and the area I found it in, because "you never know" where the ground you are detecting in might have come from originally. Good Luck and Happy Hunting!.