A look at Trading Gold Futures
Trading gold futures is a popular way to speculate on gold price movements. It is ideally suited to short to medium term trading. They can also be used to take a long term view. However, due to financing costs, there may be better alternatives.
Historical Gold Chart
As you can see from the gold price chart above, gold has been trending up since 2002. We can also see that gold prices today are similar to that high in 1981. However, the inflation adjusted gold price back then was substantially higher than today.
There are many factors that affect the price of gold. One big factor is the US Dollar. As gold is priced in US dollars, it can work effectively as a US Dollar hedge. When the dollar appreciates, gold often goes down. 
Central banks and official organizations (for example the International Monetary fund) hold around a fifth of all gold holdings. So when these institutions wish to alter their reserves it can have an impact on price.
There are many major advantages to trading gold with futures including:
The ability to short sell. If you wish to speculate that gold will depreciate over any time period, you can short sell.
There are no storage costs to consider.
The contracts can be traded on margin so you do not need to put up the full value of the contract.
Transactions can be actioned in seconds.
Comex gold futures contracts are for 100oz. Based on the current spot price of $800, this would make the nominal value $80,000. Each tick movement would be worth $10. These contracts are traded on the comex and cbot exchange.
There are also mini gold futures contracts for the smaller trader. These are 1/3 of the standard size at 33.2 oz. This contract is traded on the cbot exchange.
I will end by saying that if you want to trade gold, the commodity does provide many opportunities for speculators and investors. However, price action can be very volatile, especially during times of crisis. Prices moves in excess of 10% over the period of just one week are not too uncommon. Clearly, it is essential that margin used wisely.