Selling stock online
There are several cheap or free online trading sites such as ETrade and Ameritrade. To view your stock portfolio and manage your stocks, first sign into your account. Though each online trading site is configured slightly different, they will all have a page option that display your current stock holdings. From this page, you can click to select the stock you wish to sell. This action will lead you to another page where you can select the amount of shares you wish to sell and confirm the transaction.
Selling stock you receive
You might receive stock certificates from a loved one as a gift or via a will. If you receive a stock certificate via a will, find a stock broker who can assist you in selling the stock certificate. If you receive stock managed by a brokerage company--either from a loved one or from a former place of employment that might have paid you in stock--call the brokerage company that handles that account. Someone at the brokerage company can help you sell the stock.
One-time stock sales
If you only have one to two stocks or you don't plan on investing in the stock market at all, you should be able to take your stock certificate to a branch of your bank. Most banks have representatives licensed to assist customers with stocks, sometimes called securities. Ask for someone who can assist you with your investments. The bank employee can place a call to sell your stock and will notify you when the profits have been received. This makes sense for one-time sales, but would not be a good idea for those interested in investing.