Best Six Months Strategy - S&P 500 Chart Gerald Appel recommends an 8-17-9 MACD to generate buy signals and a 12-25-9 MACD to confirm a sell signal for a stock, which has had a strong bullish move. <img src=http://stockcharts.com/c-sc/sc?s=$SPX&p=D&st=2006-10-01&i=p85295889342&r=7211>