After a strong run-up from its latest breakout, (PCLN) appears to be acting like a true market leader typically does during its first major pullback.

From last Thursday through Tuesday, the big-cap stock dropped from 732 to 685, a 6% decline.

As far as corrections go, that's mild. But it was far enough to send Priceline below its 10-week moving average.

The 10-week moving average represents the stock's average closing price over the past 10 weeks. It helps investors grasp the stock's underlying price trend.

A rising moving average is bullish, indicating that the overall demand for shares is strong.

That's not the only function of this critical chart tool. After a stock has broken out of a base and run higher, it often takes a break and retreats near the 10-week line. The first and second pullbacks offer a chance to add shares to a winning position or establish a new one.

The best time to buy shares is when the stock is rallying back above the 10-week line and volume is fierce.

On Wednesday, Priceline's volume was 16% above its daily average, a good sign.

The leading online travel agency sports a top-flight 99 Composite Rating. Within the nine-member Leisure-Travel Booking industry group, only Expedia (EXPE) joins Priceline with a Composite of 90 or better (Expedia is a 91).

Priceline is slated to report first-quarter results on May 2. Analysts see earnings rising 48% to $3.94 a share.

While that would possibly represent a second straight quarter of decelerating growth, Priceline tends to beat the consensus view. Plus, a 48% increase in profits amid a lackluster global economy is still excellent. The upper end of the estimates among analysts is $4.11, 55% higher than a year ago.