Since the screen is constantly moving it is impossible to see every quote. Yet, you can still get a general sense of the stock's short-term direction. Another thing to note is the speed at which the transactions are occurring. If you see several green quotes in quick succession (faster than normal), it shows that there is volume behind the buying movement. Volume is one of the most important indicators of a a trend's strength. At the same time, if the quotes begin to slow down, a reversal of direction may be approaching. Low volume implies either no interest or indecision in the current trend, and it is usually best to wait until a significant trend has established itself. Lastly, the greater the size, the more influence it has. Seeing 10,000 shares being bought at the bid is more important to future price movement compared to 100 shares being bought at the bid.