Rules of Risk

The Rule of 100 – Take your age from 100. The remainder is the percentage of investments that should be in stocks.

Example #1
Take a 50-year-old woman
100-50 = 50% of your investments should be in stocks
The remaining 50% can be in securities such as Bonds, CDs or Money Markets

The rule of 25/8[1] – Any investment that makes 25% of your initial purchase price should be sold. Unless the run up is within 1 month. In that case, hold onto your investment for a few more months, watching it closely. Any investment that loses 8% of your initial purchase price should be sold immediately.
[1] http://www.investors.com/learn/S02a.asp