Review your finances to determine how much money you can afford to invest. Contact local banks and credit unions and find out what rates you can earn on the sum that you intend to invest if you buy a CD or invest in a money market or savings account. Contact investment brokers and ask about brokerage CDs because the interest rates on these securities are often higher than on bank CDs.
Divide the number 72 by the interest rates that different institutions offer to pay you on a CD or savings account. The result of this calculation reflects the number of years it will take for you to double your money if you allow your interest to compound. Investment analysts call this equation "the rule of 72," but it takes much longer to double your money if you do not allow the interest to compound.
Open a CD or savings account at the bank or financial institution that enables you to grow your money the fastest. When you open the account, explain that you want the interest to compound and that you do not wish to receive interest checks. Sign the new account disclosures and keep a copy on file in case the bank accidentally disburses your interest payments.