I like the idea of measuring the trades per second and awaiting a pace increase. To do it, I just watch time & sales. You can see how it slows and speeds up. When a stock is making a move, time & sales will simply speed up, that is, the pace of trades quickens, sometimes dramatically, so it is readily apparent. This will usually be combined with (1) occasional trades going off at a price above the current bid/ask (if it is a bull run) and (2) bid volume greater than ask volume (again, if it is a bull run).