All the math you need in the stock market you get in the fourth grade.
In stocks as in romance, ease of divorce is not a sound basis for commitment.
If you have the stomach for stocks, but neither the time nor the inclination to do the homework, invest in equity mutual funds.
You shouldn't just pick a stock - you should do your homework.
When you sell in desperation, you always sell cheap.
Never buy anything that you can't illustrate on the back of a napkin.