There is a difference between how you should clean MD finds.
There are collector coins (silver coins, wheat pennies, Indian heads, large cents, buffalo and V nickels, colonial coins, etc.) and then there is just normal pocket change stuff (1965-date dimes and quarters, non-key Jefferson nickels, etc.) the collector coins you should clean very carefully like VPNavy said, but for the modern stuff I just stick it in a rock tumbler, this gets the grime and dirt mostly off of it so they are spendable and you can spend them like normal coins or stick them in rolls and send to the bank (I wouldn't put dug coins in a coin counter since it might damage the counter, even after you've tumbled them)