Magic The Gathering...

Below is the 'official' rules about tapping as stated in the Magic The Gathering rule book. As I have had an argument about tapping creature on more the one occasion I thought I would post them here. The Magic rule book can be downloaded from the magic website.

For the sake of clarity "T:" is meant to represent tap, because I cannot copy the tap symbol.

Tapping: Tapping is the Magic game's way of showing that a card has been used. To tap a card, turn it sideways. At the beginning of each of your turns, you untap your tapped cards so you can use them again.

Activated ability. You play an activated ability by paying its cost. All activated abilities have a (":") in them. The part before the colon is the activation cost. The part after the colon is the effect you get when you pay the activation cost. For example, "T:" Draw a card" means if you tap the permanent with the ability, you draw a card.

Tap: This symbol means "tap this card" It appears in the activation costs. You can't pay a "T:" cost if the card is already tapped. Also, remember that you can't pay a creature's "T:" cost the turn it comes under your control.

Paying a cost
Once you pay a mana cost or an activation cost, there's no way to get back what you paid, even if the spell or ability is countered.

You can't pay a cost unless you can pay all of it. For example, if an activated ability tells you to discard a card and you have no cards in your hand, you can't even try to pay it.

Remember that you can't pay a creature's activation cost that includes "T:" unless you've controlled the creature since the beginning of your turn.

If an effect does something to a permanent that resembles paying a cost of it's ability, it doesn't count as paying the cost. For example, Icy Manipulator reads,
"1, "T:" Tap target artifact, creature, or land." Royal Assassin's ability reads, ""T:" Destroy target tapped creature" If you use Icy Manipulator to tap the Royal Assassin, it won't cause the Assassin to destroy a tapped creature.

Tap
To turn a card sideways. When a permanent is tapped, it usually means it's been used for the turn. Once a card becomes tapped, you can't tap it again until it's been untapped.

Creatures tap to attack. you tap lands to get mana from them. Many permanents have activated abilities with "T:" in their costs. ("T:" means "tap this permanent.")

Sometimes an effect will tap a permanent. If this happens, you don't get the effect you'd get if you chose to tap your permanent yourself.