How effective is Fibonacci Retracement tool while doing Technical Analysis of shares and stocks?

First of all, you are stating those items as fact. One thing in technical analysis that you must understand is that nothing is set in concrete. All trading is is just “probabilities”. When trading, you are trying to stack the odds in your favor. Fibonacci is only a tool to help you do that.

Next, you stated that if prices retrace off a rally to the 38.2% or 50% level and bounces that prices should go further up. What you failed to recognize is that there is also a 61.8% retracement level, so prices moving through the 50% level doesn’t mean a trend change. If prices bounce off the 38.2, 50 or 61.8% levels, then you should wait for prices to break the high set in before the retracement. In other words, say you have a stock that went from $30 to $50 and then started to drop. Fibonacci retracement levels are at $42.36, $40 and $37.64. If prices bounce off of one of those levels (are close to one of those levels), then you should wait for prices to break above $50 before initiating a long position. Granted, you can initiate a long position at one of those Fib levels, but how have you confirmed that it is only a retracement in the trend and not a trend change?

You can not use Technical analysis as a “carved in stone” if this indicator does this, then it is a buy or sell. Indicators can give false readings. That’s why you must never take a trade without a stop loss order in effect.

I’ve used Fibonacci for years and it is a very good tool, but that’s all it is, a tool. I have seen prices bounce off of 38.2, 50 and 61.8% levels and resume their trend countless number of times, BUT I do not ever say that when prices bounce of those levels that the trend WILL resume. I always way for other indicators and price action to confirm that it was indeed a reaction in the trend and not a trend change.