What EMA I should use?

I take my trading decissions mostly on 15 minutes chart. I try to read 5 mins, 15 mins and 1 hour chart but place my entry and exit level depending on 15 mins chart.I see EMA is a great indicator for entry and exit level identifying the trend. BUt I am not sure which EMA I should use on 15 min chart. I tried using 5 EMA and 15 EMA. Not yet confident. Pleaze help regarding using EMA.

Let me draw your attention to the search function at the top of the page and the bounty of pointless conjecture on which EMA to use.

http://www.forexfactory.com/sitesear...earchtype=site

WTF?? Only 3,270 pages worth?? What kind of a ripoff search function are they running around here anyway?!

21 EMA