1: Think about how much you want to invest. As a general guide, only invest the amount of money you can afford to lose all and yet not affecting your daily life. DON'T bet your house!!!
2: Understand the basic numbers and ratios. Think this way. When you want to buy a TV, you look around and compare the price, brand, design etc. Do the same with the stock. Compare the numbers. Learn to read the balance sheet. I am not saying that you should understand every lines in the balance sheet. That will be boring. You must at least know where to find important numbers like EPS, PE, Quick Ratio, Current Ratio etc.
3: You need to understand yourself. Quick simply balancing the risk vs reward. Higher risk will bring higher reward. But, everyone has different tolerance to risk. Find a level which you are comfortable with.
4: Discipline! Discipline! Discipline!
Once you have a strategy, stick with it. It sounds simple but it is not. Trust me.
When you see your stock price going down and the value of your investment falling, panic will take over and your start selling. Try to ignore the short term fluctuation.
5: Practice first before you start for real. It is always useful to practice buying and selling.
Here is a video showing where you can practice online for free.