1) save some money
2) open an account. You will have to wait until you are 18 before you can open your own account. But your parent can open an account on your behalf and it will turn over to you on your 18th birthday.
2a) full service or discount -- A full service broker will give you "hand holding" share research and give you more advice and education, but will charge you more in fees and commissions over the life of the account. A discount brokerage account you can open on-line, and you will be expected to be more independent.
3) Read some books on investing. There are a ton of books out there, some good, some really bad. I suggest "A Random Walk Down Wall Street."
don't expect to double your money quickly. Investing in stocks is a long-term play... like 30 years long term.
Don't trade for the sake of trading. I bought it at $16 last week and it is $18 today that is a 12% gain in a week. I am going to sell and buy something else... no! if it was a good buy at 16 it is probably still worth holding at 18... you will need to develop a discipline. Think about why you hold it. What id does for your portfolio, What is your holding period....
Investing in stocks can be risky. If your stocks fall 30% in value is this going to cause you distress? What is your risk tolerance?
Start with a dry run. Decide on an amount of money you might want to invest. Say $1000, for example. Pick a couple companies you know about, and invest, on paper, your thousand dollars. Follow those companies to decide if/when to buy or sell the stocks. Record the sale (or purchase) using the stocks value from the end of the trading day. (If you don't understand that, then skip it).
Have a goal in mind, like you want to double your investment, or you want to see how well you can do in 3 months. Sell and buy stocks to try to maximize return, and make only one trade on a given stock per day.
At the end of your experiment you'll either be thankful that you didn't actually invest anything because you lost too much, or you'll be kicking yourself for not using real money. Once you get the hang of it, then invest some real money.
I think a couple of the major trading sites will let you have a free hypothetical account so you can practice just like I'm talking about.
I'm 16 and want to get into stock what's the best way?