- News surprises (e.g. due to earnings warnings, analyst upgrades, business deals, market panics),
- Large blocks of stocks being bought or sold, and
- Dividends. Dividends are interesting because they are announced ahead of time to happen on a certain date. On the "ex-dividend" date any shareholder that owned the stock prior to that day becomes eligible to receive a stated amount of money per share of stock that they own. It doesn't matter if you have owned the stock for one day before or 5 years --that money shows up in your brokerage account typically a couple of weeks later on the "distribution date".
The first two are inherently unpredictable, but wiht dividends, at least the date, and usually the amount is predictable.
Because of this dependence on market action, just buying stocks to capture the dividends is an iffy deal. I will write more posts on this subject detailing some of my attempts at capturing dividends without being immediately embroiled in market action.