Hi Jimmy, great question; if by the "force" of a support/resistance level you mean, how well will it hold it, it's based on many factors... the most important is the tape reading pattern as it nears prior s/r levels (for example, 2-day high/lows, 25-day high/lows, 52 wk high/lows).

Next I look at specific market internal signals, because for example if the market's selling down hard, -1.4% from the open at 10:15am for example and taking out new 2 day lows, then I will look at the TRIN, the sector percent change from open that the stock's in, and other realtime data points, to make a "trade/no trade" decision, in realtime.

The best way to learn is to attend http://www.TradeMastery.com this March 23-24 in Vegas...

-Ken