First read this: http://stockcharts.com/education/IndicatorAnalysis/indic_RSI.html "Overbought/Oversold
Wilder recommended using 70 and 30 and overbought and oversold levels respectively. Generally, if the RSI rises above 30 it is considered bullish for the underlying stock. Conversely, if the RSI falls below 70, it is a bearish signal. Some traders identify the long-term trend and then use extreme readings for entry points. If the long-term trend is bullish, then oversold readings could mark potential entry points."
Than look this: http://stockcharts.com/def/servlet/SC.web?c=fmday , you can watch any stock and you will see RSI(14) number. More the number is lower to the 30 more you have chanses the stock will go up in the future.