If you can shoot 10 out of 10 long (CB and OB far apart) straight in shots (or more), I say that you're shooting straight. To do that, you most have a good visual alignment, stance, stroke...for that shot.
If you can shoot 10 out of 10 spot shots (from the kitchen or more) while aiming at the edge of the OB (30 degrees), I say that you're shooting straight. To do that, you most have a good visual alignment, stance, stroke...for that shot.
There are many more shots/cut angles that need to be mastered by some form of visualization or where to aim the cue. Shooting a million varied shots can't hurt, but is there a faster way?
I practice shots that I miss and often I miss that same shot the same way untilI change my aim for that cut angle. I wonder if my memory of that shot is wrong for I made that shot before many times, or is that I am not focusing at where I am aiming, did I hit the CB off center?
That I have a spot that I know that I need to hit gives me a starting point to make corrections. One needs to shoot straight at whatever you aim at to replace the GB with the CB.
It seems like I'm sarcastic, but you need to shoot straight at the right spot.
Then there comes the application of speed and English to the shot that changes where one aims.