In other words, whether the bars appear isn't determined by just one indicator; a combination of events causes them to go up or down.

Crossovers are turning points for trends. Whenever a crossover happens, whether it's the EMAs or MACD, it's likely that a trending bar will be triggered. Here are some guidelines to keep in mind:

• When the 13-day EMA crosses over the 50-day EMA, that's a clear sign of an uptrend. The 50-day EMA crossing over the 13-day signals a downtrend.

• For MACD, determining whether the crossover is going to cause a trend is trickier. It really depends on where the crossover happens (as well as on what's going on with the other indicators). If the red fast line crosses over the blue slow signal at or above the centerline, you have a trend. But if the crossover happens below the centerline, you don't. A trend doesn't occur until the lines sail up past the centerline -- and then only if the other indicators are healthy.

  Downtrends are just the flip side. The blue slow signal must cross over the red line below the centerline for it to really count.

  (Note: You'll learn more about MACD in upcoming articles. If you don't understand how it works now, you should by the time you read through Education.)