Stockbrokers, also known as registered representatives in the U.S., are the licensed professionals who buy and sell securities on behalf of investors. The brokers act as intermediaries between the stock exchanges and the investors by buying and selling stocks on the investors' behalf. An account with a retail broker is needed to gain access to the markets.
Astute readers will realise that the above guidance is mainly taking different angles to help prepare for and guide decision making by the investor. The ability to confidently make decisions is vital for investment profits and long-term success. This pdf about the decision making models of Charlie Munger (business partner to Warren Buffett at Berkshire Hathaway - both are certified investment immortals) is almost certain to prove helpful.

Dollar-cost average: This sounds complicated, but it’s not. Dollar-cost averaging means investing a set amount of money at regular intervals, such as once per week or month. That set amount buys more shares when the stock price goes down and fewer shares when it rises, but overall, it evens out the average price you pay. Some online brokerage firms let investors set up an automated investing schedule.