I second Greg's comments.
If you're new to this "game", you should learn how to play the game before playing it. In other words, paper-trading. Do your research, find some stocks you think you should buy, write their tickers and prices down on a sheet of paper, and watch to see how they do in the timeframes you're interested in.
If they don't do well, learn more, pick more, and check again.
Once you've reached a point where your paper-trades are profitable more often than not, you're ready to start *carefully* trading or investing with real money.
I'd also strongly recommend going to our homepage and reading the last 2 "Letters Home to Cousin Shorty" articles. Read them as many times as it takes to understand them. They're not only extremely amusing, in my opinion, they're also quite educational.
And perhaps soon he'll do a few that cover some of the basics for the complete newbies.
One of my favorite comments from his most recent one is that your opinion of a company matters more than anyone else's opinion does. Weigh the offered opinions, do your own research, then form your own opinion.