The most common mistakes are probably more related to money management than stock picking.

When everyone is making money in the market it is time to take profits, and reduce risk. The reverse is actually what happens.

These mistakes are compounded by listening to the Guru's of Wall Street on CNBC and CNNFN. Most of the Guru's have agenda's. The majority only have experience of what has happened during the last twenty years. 

For eighteen of those years the market has performed each year better than the preceding year. That trend is changing, yet many seem to be in denial about it. The mistake here is not adjusting strategies and expectations, based on this new reality.

Here are some of the more common mistakes!

• Getting into the market too quickly.

• Lack of training and know how!

• Incorrect measurement of risk in relation to reward.

• Inappropriate use of  margin debt.

• Lack of diversification.

• Not relating price to earnings, and therefore paying too much. 

• Pricing in unrealistic earnings growth.

• Not adjusting to the difference in the behavior of support and resistance levels in bear markets.

• Not considering the effects of monetary and fiscal policy.

• Under Capitalization

• Not using initial position sizing to positively impact the bottom line.

• Momentum trading. 

• Concentration of risk.

• Taking small profits and big losses.

• Fear of missing out, and fear of losing everything.

• Being in too much of a hurry - overtrading.

• Lack of patience, resulting in missing the big moves.

• Buying stocks that are impossible to value on any rational basis.

• Not looking for creative accounting in company statements.

• Allowing profits to turn into losses.

• Dependence exclusively on the advise of a broker

• Trading based on rumors.

• Day Trading  / Concentration of risk.

• Disregard for fundamentals.

• Holding on too long. 20% compounded annually for 5 years is wiped out when a stock loses 60% of its value overnight.