Daytraders Weekend Aftermarket Lounge 9 -12 Dec, page-90

LOL - Quick and Dirty - That's all you need sometimes!
It is more reliable when updated every 30 seconds.. but still only as useful as looking at market depth...which is not really useful!
It is just meant to be one of a number of indicators that narrow down the field of possible trades from the two thousand listed companies to 20 possibles.. I only have screen space for 9 charts so usually exclude quite a few for liquidity issues.
I normally look at number of trades & previous trades and todays volume as a percent of yesterdays..
If something does 100% of its previous days volume in the first 30 minutes it's generally going to have a good day.