Anyone can pick a stock. A monkey with a newspaper and a dartboard can pick a stock, or so I’ve been told. The goal is to buy stocks that will go UP in price. Easier said than done or everyone would do it.
There are a million or so reasons that influence a stock’s price over the short and long-term. On a day-to -day basis, the biggest influence on a stock’s price movement is generally the overall market of ALL stocks. In the short-term — most stocks move together.