My firm are beginning to make use of technical analysis for trading purposes, and the MACD is one of them. The thing is, the default exponential moving averages (EMA) are 12- and 26-day, which doesn't work for all the stocks I cover. My main questions are, why are 12- and 26-days the defaults, and also, how do you decide which trading day EMA to use when the defaults don't work for a particular stock?Thanks!!

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Not sure why the 12-26 day moving average but one tip I can give you about MACD, (I use it to trade the S&P mini contract) is that it does not work in a sideways market, you will drive yourself crazy and go broke chasing that thing when the market moves sideways. (Using a 5 min chart) Try using MACD and Key Reversal up and down, that is a good sanity check. Good luck!