I scalp the ES market grabbing most of the time 1-4 tics, maybe twice a week several tics, but overall just a few tics. I do approx 20 to 40 trades a day (I am too old to do more) so I am not one who does 150 trades a day as I have witnessed other to do. I use charting as to when to start looking for a trade and use the DOM to getting a tic or two better fills. After watching the Dom for years, I have been able to discern just a few patterns that are reliable for me, but here the thing, they occur for a few seconds, just long enough to hit the bid/ask or get in at bid/ask and takes much concentration to continually to do so, extremely draining on your eyes and I believe over long periods, very unhealthy.
Offend times the larger the volume on either bid or ask at five levels is like a magnet, but it is not total volume I watch as I see this to have little value for me, but I watch at each level if bid side at five levels have at least 1000 more than ask side levels, very good occurrence that price will go down and I need to get short if that is my original signal. If I see the ask two closest level fall under 1000 whereas the bid side maintains regular volume, price most likely will go down. "Rotation" term I use if say ask side is 1000 of more initially larger than the bid side, and price is just alternating back and forth, after maybe 20 seconds, ask/bid get even in volume then very shortly ask side has less volume, price generally goes up, I will either try to get in at bid level or hit the ask.
These are the three I use the most, there are others but they occur much less frequent and much more difficult to explain.
You can always tell when a report is due to come out, all levels drop from thousands to a few hundred as big boys pull there orders.
But I think if you are a trend trader, this intense style will not matter, and yes, there are times that above doesn't always work or huge orders comes in and I am not quick enough to take advantage, once market has gone away from me 2 tics, I have to pass on the trade.
I am sure this works in all other markets, but at even a more quicker speed, and in some markets like crude oil, it is almost impossible to be quick enough to take advantage.
I don't recommend to anyone to scalp, I just never found a consistent way to day trade ES by trend. There are much other better markets to day trade for trend trading like currencies and crude oil. Also, if you are retail trader, I have never seen anyone scalp successfully paying retail costs.