Winston846:
Without turning this into YAAT ("yet another aiming thread"), I'll answer that the same technique is used. Let me guess as to why you're asking this question -- you always overcut these "not quite perfectly straight-in" shots, right? That's parallax error -- you're estimating how much offset from centerline to aim the shot, and it turns out to be too much.
My suggestion would be to line up a series of long straight-in shots (diagonally across a 9-footer, placing the object ball on the centerspot of the table [between the two side pockets], and placing the cue ball near the corner pocket, but leaving enough room away from the pocket aperture itself where you can bridge comfortably). Shoot a series of these shots using the method described above, until you can't miss (or miss only occasionally -- we're not robots, afterall). Then, either alter the position of the cue ball slightly, or alter the position of the object ball slightly (former is preferred), and shoot that shot until you can't/only-occasionally miss. Then, adjust again, moving the shot just slightly further off a perfectly straight-in shot. Keep adjusting the position of either the cue ball or the object ball until you get to a three-quarter ball hit, and methinks you'll then be past your nemesis, for you are now dealing with no-doubt-about-it cut shots.
This is one of my favorite drills to warm up, by the way. I'll hit these with varying amounts of power, follow, draw, etc. The most difficult execution of this shot is to hit it with LAG speed -- j-u-s-t hard enough to have the cue ball lightly contact the object ball, and that object ball lags to the pocket, and j-u-s-t falls in. That's a real tester of your fundamentals, that's for sure!
Hope this is helpful!
-Sean