there is a problem with your question....you don't tell us what type of trading that you do...is it day trading or longer term.
I find it makes a difference.
For Day trading (intra-day trading) I find that the the signal line is reasonably useful though it still gives many many false alarms...but I don't day trade so my comments there are moot.
From the sounds of things you are looking at individual vales of MACD and not the trend...When I use MACD I eliminate the signal line as it complicates things...Here I'll show you
http://farm8.staticflickr.com/7249/7657152530_317be350e0_b.jpg
looking at this chart which is pretty bare bones right now... the first MACD Chart MACD(1) shows buy signals on DEC 21...again on Jun 2 (crossing the zero line)...potential sell signal on Feb 1...definite sell signal on Feb 14...Buy signal on March 13...sell signal on March 28...confirming sell on Apr 20...buy signal on May 24...confirming buy on Jun 18 and sell on July 2.
The Second Chart MACD(2) is not much better....without the signal line I trend the MACD line by drawing a straight line linking the high and low trends
In both cases I find the MACD very difficult to predict and make decisions...It has a lot of noise in the chart for me.
However if you combine MACD with Bollinger Band (BB) overlay and its corresponding indicator BBwidth and Slow Stochastics (note the 30 day look-back)
Suddenly the whole picture changes
http://farm9.staticflickr.com/8433/7657155940_8c6bcda001_b.jpg
In the same time period you see only 2 buy signals (Blue verticals) with the second is more of a confirmation... One sell sign (red vertical) and one indication of a bottom (Green vertical)
I use the Green vertical as an indication for exiting a short position
So how does this work:
1 Buy signal - the SIMULTANEOUS positive slope of MACD, BBWidth and Slow Sto
2 Sell signal - the SIMULTANEOUS negative slope of MACD, BBWidth and Slow Sto
3. Bottom signal - simultaneous rise in trend for MACD and Slow Sto with a neg slope to the BBwidth
The bottom is not necessarily the absolute bottom...rather it is an end (maybe temporary) to the fall of share price....ie. A REASON TO EXIT A SHORT POSITION
You can see a false sell signal on June 24...see how the Slow Sto rises to destroy the signal.
Test this chart before you believe me but this is a pretty reliable chart and is my goto chart for BUY/SELL signals.
You won't find this in any book but rather it is the result of years of research on my part.
Hope you find this useful.
EDIT @MD what are you talking about NORTEL does not exist as a company anymore