In addition to reducing/eliminating slack - better mending, I have found it helpful to 'anticipate' the strike and which 'direction' to move the rod to set the hook. For example, if drift is from my left to my right I try to 'anticipate' setting the hook and 'remind' myself to be prepared to move rod to the right. In other words, set the hook in the direction of the drift rather than straight-overhead or in direction opposite of the drift. Setting the hook in the direction of the drift usually means you're 'pulling' the fly into the trout's mouth, rather than away from the trout by trying to set the hook in the direction away from the drift or coming up straight-overhead.
I do not take any credit for the hook-set-in-direction-of-drift approach; if memory serves, that was a tip I got from Walter Babb 'many moons ago.'