When to buy and sell stocks

In my own opinion, I think doing enough research will be an important factor to decide when to buy and sell shares.. Are there any news that will affect the price movement of the stock? Is the news already factored in the current price already? Also during earnings seasons, the financial results will affect the stock price movement more. If the earnings are good and better than expected, it may be time to sell the stock if the price increase already reflects this. But if not, we can consider to buy the stock if the stock price is still undervalued.