The smart way to invest is not to try to time the market at all.
Oh sure you can see how a well timed investment might make outlandish sums of money , but you can also see how a poorly timed investment will loose a lot.
If that guy had understood Dollar cost adverageing he would have invested $200 six years ago and it would have slid rapidly to the value of $150 or so , but then he would have bought $200 the following month and the next and the next and so on.
If he kept that up till now he would have made a good investment by buying the advradge price of stock inbetween that time and this , since there was a big dip early in this program he got a bargan buy at that time and whenever the stock market was high he naturally bought fewer stocks because he bought the same dollar value reguardless of the swing.
Dollar cost adveradgeing is a good simple way to make buying low automatic because when stocks are low you tend to buy more and when they are high you buy no more.
Selling can be done the same way , retireing people take note, when you retire you can cash it all in at a market high for a fantastic profit , or perhaps regret this when the market rises again, or you can sell a bit at a time selling at a rate intended to get you out of the stock market at about the time that you die.
NO one knows exactly when they are going to die , butr actuarial tables can give you a good idea of what is likely , simularly no one knows the day to day direction of the market , but a study of trends can give one a good idea of what is likely.