Error Guessing is described in ‘Testing Computer Software’ by Cem Kaner :
“For reasons that you can’t logically describe, you may suspect that a certain class of tests will crash the program. Trust your judgment and include the test.”
This quote suggests to me that there is an informal model in the tester’s head and that the subconscious is applying a strategy to the model which the tester is unaware of. The tester is only aware of the subconscious flagging the results of that check to the conscious as a nagging doubt.
If you do engage in error guessing then you should be aware that:
- you have a model and applicable strategy in your head that you are not using on the project or possibly even aware of.
- if your strategy does work then you should try to quantify it so that you can use it consistently.
- If it doesn’t work then you should possibly change the model and strategy in your head.
 Testing Computer Software, Cem Kaner, Jack Falk, Hung Quoc Nguyen, 2nd Edition 1993, International Thompson Computer Press