Quote from Dogballoon:
Well, I don't really scalp anymore. Only when the situation calls for it, when I do not have a read, $trin indicates a boring market, and there are no longer setups in any of my stocks. My plan is based on the chart, but my read (when I enter and how aggressive the buyer/seller is, where he is resting, etc.) comes from scalping the tape in the past.
It's important to not just focus on size, but on spreads and prints, and even how the ECNs behave on the inside. Moves begin one way when the big fish test the market to see if there is anyone else around who will fill them, and then behave differently when pushing through low volume areas looking for the opposite side. When they end, you often see the size appear.
Even more important is to choose a particular market and focus on it for a long time, until you see how it reacts to its sector and the larger market, and any secondary stocks in that sector. If you were trained to just jump in front of size, you're probably being taught that only so you can rack up commissions and then leave, which isn't in your best interest.