All of the following Monopoly rules come from the official game instructions that have accompanied standard U.S. Monopoly sets since 2008. If they differ from the way your family plays, that's perfectly fine, since Monopoly has always fostered a rich culture of "house rules."
The object of Monopoly is become the wealthiest player by buying, selling, trading and collecting rent on properties. Depending on how long you want to play, you can either play until all but one player has gone bankrupt or set a time limit and crown the richest player the champion.
To start the game, each player chooses a token and one player is selected as the banker. The banker distributes $1,500 in Monopoly money to all players: two $500s, $100s and $50s; six $20s; five each of $10s, $5s and $1s.
The highest roll of the dice goes first. Start in the GO square and move clockwise around the board according to the number on the dice. If you land on an available property, you can buy it by paying the banker the price listed on the title. The advantage of owning property is that opponents have to pay you rent when they land on your square. If you buy all of the properties in the same color group, then you have a monopoly, allowing you to charge double the listed rent. Once you have a monopoly, you can start to build houses and eventually a hotel, raising the rent further. Of course, you have to pay rent whenever you land on an opponent's property.
If you land on an available property, but decline to buy it, then the banker can auction the property to the highest bidder. The banker starts the bidding at any price and all players can participate, including the banker and the player who originally declined the property.
You can get sent to jail three ways, by landing on the square marked "Go to Jail," by picking a "Go to Jail" card or by throwing three doubles in a row. You can also get out of jail three ways: using the "Get out of Jail Free" card, rolling doubles on one of three consecutive turns or paying your way out with $50. If you don't roll doubles after three turns, you have to pay $50 to get out of jail. While in jail, you can still buy or sell properties, build houses and hotels and collect rent.
Trading and private sales of properties between players is not only legal, but highly encouraged. The only thing that players cannot do is give private loans. Only the banker can mortgage a property. The fixed interest rate for "lifting" a mortgage is 10 percent of the price on the title.
A player goes bankrupt when he or she doesn't have enough cash or assets to pay the bank or another player. Players can sell houses and hotels back to the bank for half of their original value -- but if that doesn't provide enough cash, the bankrupt player forfeits all properties to the bank or an opponent and is out of the game.