Interesting point from a Motley Fool column earlier today:
Consider this approach instead: Sell your stocks when you want to buy a house, furniture, or other major purchase. Sell when you have too much in stocks and you want to buy some bonds, gold, or collectibles. Sell when you have too much in any one stock. But sell a stock, or a dicey market like this one, on valuation alone, at your own peril.
Basically, what he says is buy and HOLD HOLD HOLD ... and if you do sell, make sure you really have a very very very very darn good reason to sell apart from just getting off the table ... easier said than done i'd say ... but then guys like Buffet have had so much success, there must be something to it !!