There are two main types of scrupulosity. Father Thomas Santa (writer for Scrupulous Anonymous) states that scrupulosity consists of believing that venial sin is mortal when it is not. Second, believing that no sin is venial when it is not.
From my experience, I believe that there are two stages of conscience correction. The first thing that a scrupulous individual should do is resist the temptation to think that venial sins are mortal. There is a special way to overcome this type of temptation. The simplest criteria I found in distinguishing venial from mortal sins was in a Scrupulous Anonymous article entitled ‘Was it a Mortal Sin?’ It is a quite simple criteria, that is not particularly stressed often: A mortal sin requires “full knowledge,” which means that if you have a doubt that a sin might be mortal, it is therefore not mortal. Mortal sin means that you are 100% certain that it is mortal. If there is any doubt, that means you do not have full knowledge and therefore can absolutely believe that you have not committed a mortal sin. This is a very powerful piece of advice for the scrupulous. Once this correction is made, there is a need to correct a scrupulous individual’s perception of venial sin vs. no sin.