Professionals trade according to a plan that is thought out in advance. That plan is based on market action for their chosen time frame.
The only true way to measure if a stock is behaving as it should is with technical analysis.
For longs, stops should be placed just below the most recent support. I like to use a 10-day chart using 10-minute bars for finding that support for a swing trade.
For longer-term trades you would look at levels on a daily or weekly chart.
For shorts, stops should be place just above a recent resistance level.
Source: Yahoo Finance
http://finance.yahoo.com/news/heres-the ... 25829.html