One of the most popular forex indicators is the Relative Strength Index (RSI), which determines the strength of the currency pairs you are following over time. This is one of the forex indicators you can use to see if a particular currency pair is oversold (less than 30) or overbought (above 70) and take a position accordingly. The RSI is one of the primary forex indicators used in many trading systems and is typically combined with others to predict a good time for a trade.