Support And Resistance Levels   

Support and resistance represent keys where the forces of supply and demand meet. In the financial markets, prices are driven by excessive supply (down) and demand (up). Supply represents bearish & selling. Demand represents bullish & buying. As demand increases, prices advance and as supply increases, prices decline. When supply and demand are equal, prices move sideways.

Support: 

Support is the price level at which demand is thought to be strong enough to prevent the price from declining further. As the price declines towards support and gets cheaper, buyers become more inclined to buy and sellers become less inclined to sell. By the time the price reaches the support level, it is believed that demand will overcome supply and prevent the price from falling below support.
graphic
Support does not always hold and a break below support signals that the bears have won out over the bulls. A decline below support indicates a new willingness to sell and/or a lack of incentive to buy. Support breaks and new lows signal that sellers have reduced their expectations and are willing sell at even lower prices. In addition, buyers could not be coerced into buying until prices declined below support or below the previous low. Once support is broken, another support level will have to be established at a lower level.
Support levels are usually below the current price, but it is common for a security to trade at or near support. Technical analysis is not an exact science and it is sometimes difficult to set exact support levels. In addition, price movements can be volatile and dip below support briefly. Sometimes it does not seem logical to consider a support level broken if the price closes 1/8 below the established support level. For this reason, some traders and investors establish support zones.
Resistance 

Resistance is the price level at which selling is thought to be strong enough to prevent the price from rising further. The logic dictates that as the price advances towards resistance, sellers become more inclined to sell and buyers become less inclined to buy. By the time the price reaches the resistance level, it is believed that supply will overcome demand and prevent the price from rising above resistance.
graphic
Resistance does not always hold and a break above resistance signals that the bulls have won out over the bears. A break above resistance shows a new willingness to buy and/or a lack of incentive to sell. Resistance breaks and new highs indicate buyers have increased their expectations and are willing to buy at even higher prices. In addition, sellers could not be coerced into selling until prices rose above resistance or above the previous high. Once resistance is broken, another resistance level will have to be established at a higher level.
Resistance levels are usually above the current price, but it is not uncommon for a security to trade at or near resistance. In addition, price movements can be volatile and rise above resistance briefly. Sometimes it does not seem logical to consider a resistance level broken if the price closes 1/8 above the established resistance level. For this reason, some traders and investors establish resistance zones.Methods to establish support and resistance:

Support and resistance are like mirror images and have many common characteristics. 

Highs and Lows:
Support can be established with the previous reaction lows. Resistance can be established by using the previous reaction highs.
Support = Resistance
Another principle of technical analysis stipulates that support can turn into resistance and visa versa. Once the price breaks below a support level, the broken support level can turn into resistance. The break of support signals that the forces of supply have overcome the forces of demand. Therefore, if the price returns to this level, there is likely to be an increase in supply, and hence resistance. The other turn of the coin is resistance turning into support. As the price advances above resistance, it signals changes in supply and demand. The breakout above resistance proves that the forces of demand have overwhelmed the forces of supply. If the price returns to this level, there is likely to be an increase in demand and support will be found.
Trading Range
Trading ranges can play an important role in determining support and resistance as turning points or as continuation patterns. A trading range is a period of time when prices move within a relatively tight range. This signals that the forces of supply and demand are evenly balanced. When the price breaks out of the trading range, above or below, it signals that a winner has emerged. A break above is a victory for the bulls (demand) and a break below is a victory for the bears (supply).
Support and Resistance Zones
Because technical analysis is not an exact science, it is sometimes useful to create support and resistance zones. Each security has its own characteristics and the analysis should reflect the intricacies of the security. Sometimes exact support and resistance levels are best and sometimes zones work better. Generally, the tighter the range, the more exact the level. If the trading range spans less than 2 months and the price range is relatively tight, then more exact support and resistance levels are probably best suited. If a trading range spans many months and the price range is relatively large, then it is probably best to use support and resistance zones. These are only meant as general guidelines and each trading range should be judged on its own merits.