Rich, I use a trailing moving average system that "more or less" cuts the mid-point of a cycle between the low and the high or high and low. Looking at the numbers that the moving averages are working off of and doing a little mathamatics, I can pretty well calculate (or guess, if you will) where (aproximately) the anticipated cross is going to occur. That point, measured from the last high (or low) gives me a target for where the price of the stock is going.
My system is set up for swing trading, not for day trading.
In the case of MRK, I got a cross at 38 3/8, measured off of the high on August 23rd (at $47) and that was halfway to the low of 29 3/4 on October 11th. Now IF my moving averages re-cross on the little plateau that MRK sat on between October 7th and October 29th, and if that is halfway down (measured again off of the August 23rd high at $47) then that would set a target price of $16 or so.
Susequent events can skew the target, if MRK rallies suddenly and the re-cross, that I am anticpating, doesn't occur, then I don't have a signal, so I look around for another stock, to play. I have 2700 stocks in my data base.
Jim