As not many responses have provided specific points regarding aspects of the stroke and how they effect aiming, I'm provide some of the DO NOTS, which certainly are stroke errors that send the OB off the aim line.
On near straight in shots, applying unintended side english throws the OB offline. On slow shots the throw effect increases, as does swerve on the CB, further messing up the shot. On firm shots, throw is less, swerve is far less (unless the CB is hit high) and depending on one's bridge position relative to the cue's pivot point, deflection could counteract or add to the error. Bridging a little longer than one's pivot point can reduce and even cancel out the effects of such stroking errors.
On cut shots, applying unintended outside english can throw the OB significantly off the intended path. Conversely, unintended inside english often has negligible effect on the OB path. So being careful to hit center or slightly inside can be a way to avoid the stroking errors that result from unintended outside english.
Swiping: When we see cue actions that swipe, it is often assumed this changes the direction of the CB significantly. I suggest people aim at a mark 7 feet away and swipe some shots, hitting near to CCB as slow and firm speeds and see what swiping actually does. Experiment with bridge lengths too and see how that effects any change in direction of the CB due to swiping.
These effects are complex and interrelated, hence they're typically thought of as a forbidden zone and the mysterious cause of many wrongs. Hence they make great excuses for missed shots. If we understood them better, and used our smarts to reduce their influence, we could relive ourselves of a great deal of pressure regarding perfect stroking and focus upon the main causes of missing shots... i.e. Bad aiming via incorrect bridge V placement.
