How do you know an investment is probably safe...?

I don't know much about investing except buy low and sell high, but I do know one thing. When you see an article like this.

Fannie Mae posts loss, to cut payout, raise capital

And then the stock goes up 8.91% you are probably holding something that has hit bottom. Plus if it drops 20% the next day you are really only out 11.09%.

I'm kicking myself because I almost bought some more AMD, just a small amount (<1% of my account) and it went up today by 9.04%. Looks like I might finally recover some of my losses in AMD so my account is feeling good today, but as usual, tomorrow is another day and it'll probably be down again. It is really nice to have an account that I don't take too seriously.