When you are investing in the stock market, you have to determine your acceptable level of risk. A lot of this will depend on your age, your bank balance and your personality.
Safe but Slow Investment Bets

Tbills
Savings Accounts
Money Market Accounts
CDs

Riskier, with Growth Potential

Real Estate
Stocks/Bonds
Mutual Funds

Very Risky, Very Lucrative

Stock Options
Starting Your Own Business