Penny Question....

For me I flip them like you are playing "Heads or Tails" Copper has a High Pitched sound and Zinc has a quick ring and then silent. You can practice by flipping a known copper penny (ex 1981) and the flip a 1983 Zincoln. You will notice the difference. Its quick and easy.

One suggestion I saw somewhere I really liked was to make a two sides scale like a seesaw and balance it with a date you know what the content is. Its reaction will give you the answer. The nice thing about that is you can make some pretty crude versions of it with things you can usually find laying around instead of always having to have a scale present.

The sound the coin makes is a good way to tell the difference but the best way is to check their weight. Copper cents weigh about 3.11 grams and zinc cents weigh about 2.5 grams.

Dropping any coin to hear a difference in a ring is usually mentioned by those that are not coin collectors. Nothing like having a coin hit a hard surface. And also, may not work at all if your a bit hard of hearing.
As has been posted so many times now a popsicle or ice cream bar stick is the best and cheapest way. All you need is a bit of glue, the stick and a pencil. A standard, six sided pencil is best. Simply take the stick and place it about half way so it balances. Now drop a bit of glue at that spot on the pencil so the place stays the same. When dry do one of two things.
1. Place a not to worn Cent with a date way AFTER 82 at one end of the pencil. Now place any 82 in question at the other end of the pencil. If it balances, the 82 is a Zinc one. If your 82 makes it fall, it is a Copper one.
2. Do the opposite. Place a well PRIOR to 82 Cent at the far end of the stick. Now place your 82 at the other far end of the stick. If it balances, yours is a Copper one. If yours does not make the sick move, yours is a Zinc one.
Always remember to eat the stuff on the stick first.