What products or companies do you already use, or like? Whatever you're interested in following, perhaps buy a couple shares from them. This is a learning experience.
Since you are under 18 your dad would probably have to open a custodial account for you.
When you buy a stock you can make money in two ways.
1) if the stock pays a dividend (FYI - Google does not currently pay a dividend.)
2) when you sell the stock. If the price of the stock is more than what you paid for it you make a profit, however the price can also go down and you could take a loss.
Don't expect to get rich quick. Stocks work well with investing over time.
Consider stocks that pay a dividend where you can reinvest the divided and purchase more shares with the money that they pay you.
You need to decide what is your risk tolerance - since you are young you should have a higher tolerance for risk because you have more time to earn back any losses.
If you want to play it safe consider stocks that sell consumer staples. Staples are things that people will buy even in a recession - shampoo, laundry detergent, toilet paper, soup.
Go do some research and learn about mutual funds and exchange traded funds (ETFs) - you can make one purchase and buy several stocks at once.
Go to your local library and see what books they have in the investing section. Try watching shows like Mad Money on CNBC or Nightly Business Report on PBS.
Take that $100. and subscribe to Forbes Magazine and the Wall Street Journal. Read every article on every page. Go to Yahoo Finance. Read. Go to Motley Fool. Vanguard. Fidelity.
Educate yourself on stock market history. Read about the Great Depression. Read about the Black Octobers. Read what happened to Bernie Madoff. Enron. Fannie Mae. Freddie Mac. Sears. Polaroid. Kodak. AIG. Washington Mutual. among, many, many others.
Your early investing mistakes are the costliest.
45 years ago, I had $3000. I bought speculative stocks. The money was all gone in less than 2 years. WHAT IF I had bought Coca Cola, reinvested the dividends and held on??
When you invest in stocks, you buy a small portion of the company. You might find it easier to get your head around if you think about it this way:
You buy stocks, and basically give free money to the company, they invest your money in their own company and give you a small percentage of the company's profit. They also give you a small share of the profit because they don't want you to sell the shares, when no one sells the shares, the share price goes up (usually), then the company can create more shares and sell them. For this to work they must reward people who keep shares.
So I am 15 years old, and my father approached me saying he would give me a hundred dollars to play with in the stocks to learn something. Now all I know about stocks is that if I buy a stock in Google, and then something that I don't quite understand happens, than I profit somehow. Can someone explain to me how it works, and some general tips in when and who to invest in ?