Some people think that the right time to sell your stocks is when the stock’s value goes down but in a certain point it again goes up then on another week it again goes down. In this case, it is so hard to decide when to really sell your stocks. When the stock value is about to drop your broker will advise you to sell it. 

An investor sells his stock when he has already reached his financial goal. This is what the person does when their only reason for investing is to sell their stocks when they reach their retirement and transfer their money into safer investments like saving it on the bank. Buying a house or a car or sending you kid to college are also the reasons for selling your stocks. 

The next major reason to sell your stocks is when the stability of the company where you invest is at stake. If there are many changes in the business you have chosen to invest in it also affects the value of stocks to drop and be unstable.
 
If the value of your stocks goes up or if the money you have invested doubled it is also a perfect time to sell your stocks. You will never know on the next days ahead it might go down again.

Being a new investor, you have to consult a broker who is more knowledgeable than anybody in terms of stock market. They will surely help you decide before buying or selling your stocks.

A common stock is what you hear quite often. The common stock can be purchase by anyone regardless of their age, income and financial standing.  common stock , basically you will be a part owner in the business you are investing in.  As the company grows and earns money, the value of your stocks rises.  If the company does poorly or goes bankrupt, the value of the stocks falls.  Common stock holders do not participate in the operation of the company but they do have the power to elect to the board of directors.  They also have the rights to attend to stock holders meeting.

There are also different classes of stock.  The different classes of stock in one company are often called Class A and Class B.  The Class A stock gives the stock owner more votes per share than the owners of Class B.  A lot of investors avoid stocks that have more than one class and stocks that have more than one class are not called common stock.

Preferred stock is a mix of a stock and a bond. The owner of the preferred stock can lay claim to the assets of the company in the case of bankruptcy and proceeds to the profits from a company before a the common stock owners.  The disadvantage of this is that the company typically has the right to buy the stock back from the stock owner and stop paying dividends.