Geography/History
500 is an extension of Euchre and was originally invented in the United States by the United States Playing Card Company in the early 1900s but now mostly played in Australia and New Zealand.

500 is largely a social game and has not attracted the deep tactical analysis of bridge. Tactics often revolve around using various means to indicate to one's partner information about the hand one possesses, including agreements to make certain bids depending on whether one possesses specific cards (rather than on what the player believes they can realistically win), and surreptitious signals (by the tone of voice, exact words used to indicate bids, and so on).


Setup
There are many variants to 500, but the "standard" deck has 45 playing cards, the 2's, and 3's, being removed, and a Joker being added (In Australia, the Joker is called 'the bird', as in Australian 500 decks this card features a Kookaburra rather than a jester). Alternatively, a 43 card deck can be used. In a 43-card game, the black 4's are also removed, and the widow consists of only 3 cards. Players play in pairs, usually diagonally opposite each other. To begin a hand, 10 cards are dealt to each player, and the remaining five cards (known as the "widow," the "kitty" or the "blind") are placed in the center of the table. Traditionally, the deal is performed by dealing three cards to each player, then placing three cards in the widow, four cards each and two to the widow, and then three.

The standard game described above is the setup and deck for the most common 4 player (Two teams of two) variety of 500. Variations exist, with appropriate additions or deductions to the deck for playing 3, 5 or 6 handed 500. 3 handed uses no teams, 5 handed teams rotate and each player takes a turn without a partner, 6 handed can be played as either 3 teams of two or two teams of 3.

As in Euchre, in non-trump suits, the order is the normal Ace high-King-Queen-Jack-10-9-8-7-6-5-4 low, but in the trump suit, the highest card is the jack of trump, called the right bauer. Bauer, often anglicized to bower, is the German word meaning farmer, peasant, or pawn. This name is often used to refer to the jack of German games. The second highest (even higher than an ace of trump) is the jack in the suit of the same color, called the left bauer. For all intents and purposes, the opposite jack is considered as if it were part of the actual suit. This is important later in the game, and is usually known by newcomers as the hardest part to learn about the game.


Bidding
After the deal, players bid in turn. A bid indicates that the player believes he and his partner together will win a certain number of tricks and that a certain suit will be trump for this hand. For instance, a bid of "seven spades" indicates that the player wants to attempt to win seven or more tricks with spades being the trump suit. In American play, a bid of six is called an "inkle." A player who bids "inkle spades" is indicating to their partner that they have some spades, but not enough to bid seven. Only the first two players may inkle. The player may elect not to bid, called "passing". Bidding proceeds clockwise around the table, and each subsequent bid must be a higher-scoring bid (see the scoring table below) or the player must pass. A player who passes cannot subsequently make a bid in this hand. Eventually, all but one player will pass and the bid is decided. In American play, there is only one round of bidding, with each player getting only one chance, in turn, to either bid or pass. The player making the successful bid then collects the widow. This player sorts through his hand and discards the least-useful five cards (possibly including cards picked up from the widow), and places them face down; the discarded cards playing no further part in the hand.

If nobody makes a bid, there are two variations. Most commonly, the hand is declared dead and a reshuffle and redeal is made, but some games are played where no bids mean the round is played as no trumps, and scoring is 10 points per trick.


Special Bids
No trump means that the joker is the only trump card (there are no bauers when playing no trump). 
A Misère (also called Nullo or Nello) bid means the bidding player is trying to lose all ten tricks. If playing with a partner, the partner folds their cards and does not participate in the round. 
Open Misère is the same as misere except the player playing this bid must reveal all of their cards to their opponents after the first trick. 
Double nullo is an American variant in which both players of the bidding team play and must lose all tricks. This is also called Grand nullo, which is often corrupted to Granola. 

Gameplay
The game focuses on tricks. The lead starts with the player to dealer's left, and this person plays the first card. In some variations, the lead play is made by the player who won the bidding. All players must follow suit (yes, even the left bauer if trump is lead, and it's the only trump a player has). After all four have played, the highest trump takes the trick, and receives the honor of leading the next. If no trump came out, the winner is the player with the highest card of the suit that was led. Once all ten tricks have been played, the hand is scored. The player to the left of the previous dealer then becomes the dealer for the next hand, so that the deal moves clockwise around the table.

In no trump games, the only trump card is the joker and it has no suit. There are no bauers and all the jacks fall between the queen and ten of their respective suits. Players must always follow suit and may use the joker to trump a trick only if they cannot otherwise follow suit. The joker may be led, in which case the player immediately nominates the suit and players must play according to that suit.

In some variations, the person that won the bid also has the option to 'Declare'. This entitles the winner of the bid to receive one card from their partner after discarding from the widow or blind. The partner picks their best card and hands it to their partner face down. The winning bidder must then discard one additional card so they only have ten cards. The winning bidder now plays against the opponents without the assistance of their partner and must take all ten tricks. If they are unable to take all ten tricks then the score is -500 (negative 500).


Goal/Scoring
The goal is for the team who won the bid to take at least as many tricks as they bid. If the high bid was "eight hearts," then the team wins the hand if they take 8, 9, or all 10 tricks and are awarded points according to the table below. If they do not make their bid, that number of points is subtracted from their score. The other pairing is awarded 10 points for each trick it won regardless whether the other team made their bid.

A team wins by winning the bid and scoring at least 500 points; for example, a team with 490 who does not win the bid cannot win a couple of tricks (and the associated 10 points per trick) and say they have won. A team whose score dips below -500 points loses the game. This is also known as going "out the back door."

                Spades    Clubs   Diamonds     Hearts    No Trump 
6 tricks      40            60               80                 100             120 
7 tricks     140        160              180                200             220 
8 tricks     240        260              280                300             320 
9 tricks     340         360              380               400             420 
10 tricks   440         460              480               500             520 
Misère:    250 
Open Misère: 500 

If a team wins all 10 tricks and the bid scores less than 250 (or did not bid) the team gets 250 points.