Rules of trading are different than rules of investing but there are many similarities.  If you are a trader, be careful and maintain discipline.  Here are my 10 rules that you should never violate: 

1. Define how much you are willing to lose before making a trade.  Set a defined dollar and percentage stop before you make the purchase.
2. Know what you are buying and why you are buying it.
3. Never buy something just because someone else said to buy it.  Do your own research.
4. Define where you want to sell. 
5. Don’t place all of your bets in one day.  Phase into a position.
6. Keep reasonable expectations.  Don’t be too greedy.  Remember, pigs get fat and hogs get slaughtered.
7. Never buy a stock that has made strong advances on two consecutive days.
8. Never short a stock that has made strong declines on two consecutive days.
9. Be aware of established support for a stock and buy as close to that point as possible.
10. Know why you are breaking any of the above rules.