That is certainly a great question, the answer to which is surprisingly simple: there is almost always a good time to be in stocks if you know which ones to buy and when.
The "almost" qualifier has to do with those times when the general stock market is going through one of its bearish phases that happen every 8-10 years, although smaller corrections dependent upon global developments can happen at any time too. Those, however, should be used as an opportunity to buy. Some recent examples of such circumstances are the Russian financial debacle of 1998 or the Asian crisis of 1997.
Buying stocks when the economy is about to enter a recession period is one of the worst times to enter the stock market. It is advisable to wait 18-24 months after the recent peak in the stock indices to buy into stocks.
If there is one truly best, golden, way to trade stocks it is a safe way. The safety in question has to do with the fundamentals, be it the fundamentals of the entire economy or a particular stock. It is for this reason that you want to abstain from holding stocks during a general recession, as noted above. It is of equal importance to to buy stocks that are fundamentally sound and the best time to do it is when they happen to be depressed, preferably because of general market conditions.
Relying on fundamentals seems to be somewhat of a forgotten art as these days most trading in stocks is based on technical indicators. If only for this reason, taking into account fundamental indicators can give a trader a considerable edge.
Successful trading requires one to be selective, an element that most beginners and oftentimes even more advanced traders tend to ignore. There are really not that many good opportunities out there, so being choosy in one's decisions helps weed out poor candidates. It is in this respect that fundamentals come in handy again.
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