KDbridge - Leads and Discards Opening Leads and First Discard
Rusinow Leads
We use Rusinow leads, which means that we lead the lower of touching honors.  For example, if we decide to lead a suit headed by the KQJxx, we will lead the queen.  Rusinow leads go down to the 9 spot, which would promise the 10.  We also continue to use these leads throughout the defense of the hand.  By necessity, if we decide the best lead is a doubleton honor, we must lead low, because the honor lead would promise the next higher card above it.

Parity Ace-King Leads
When we lead either the ace or the king of a suit, we decide which one by counting the number of cards in the suit.  With an even number we lead the ace, and with an odd number we lead the king.

Why?    Every hand has either three suits with an odd number in them and one suit that has a even number, or three suits with an even number, and one suit that has an odd number of cards.

If partner leads the king from ace-king promising an odd number, and both the dummy and I have an odd number, than I know that declarer must have an even number in that suit.  If it is discovered later that declarer has a second suit with an even number, than declarer must also have a third suit that has an even number, and the remaining suit will have an odd number.  Parity leads can help defenders quickly determine the shape of declarer's hand.
    An example:

    The contract is six spades, and your partner leads the K - That's a Parity Lead, which promises and odd number of hearts.  The dummy also has an odd number, and you do, too.  So how many does the declarer have?  Does declarer have an odd number of hearts, or an even number?  He has to have an even number!  Three hands have an odd number, so the hidden hand must have the even number.

    After you follow suit with the 2, the declarer drops the Q.  Hmmpf.  That's a false card!  He cannot have a singleton, so he has another one, right? 

    You must play the 2, which is either a singleton or an odd number.  (With three hearts in your hand, give your partner count... play up-the-line to show an odd number.)  If you show an odd number, as well as the dummy, your partner should be able to see that she can cash the next top heart.  (If she doesn't, declarer's attempted false card will work, and he will make the slam.)

Odd/Even Discards
There are three very popular methods used to give partner a suit preference signal.  The signal card is played when a player makes the first discard.  The older method is referred to as Standard and is very simple.  A second method is the Lavintal method, and is an improvement over Standard.  The third, and perhaps the best way, is called Odd-Even discards.  We use Odd-Even discards.

The ACBL has a regulation that these discards may only be used at the first opportunity to discard, but it seems to be regularly ignored by almost everyone.  Even so, it's the first discard that is the most important.
    Odd Card
    At the first opportunity to discard, usually when declarer is drawing trump, the discard of an odd-pip card, such as the 3, 5, 7 or 9 suggests that you would like partner to lead the same suit you are discarding.

      Odd encourages - Lead the same suit

    Even Card
    The discard of the 2, 4, 8 or 10 at the first discard discourages the lead of that suit, but is also a Suit Preference signal.  A low and even spot card asks partner to lead the lower of the two remaining suits, while a high and even card asks for the higher suit.

      Even discourages, and is also a suit preference signal

The 6 - No Signal
Note that the 6 is not included in this group of signal cards.  Why?  Because it cannot be interpreted as either a high-even car nor a low-even card.  The best you can use it for is to say, "Partner, either I do not have a card that I can signal with, or I have no preference."