On Sati-Sampajanna

So if I am mindful of let's say a sensation or I am just mindful of a specific body part should I label that "event", e.g.: thinking, thinking, touching, touching, seeing, seeing? I am asking because the buddha also said that one should use sati in tandem with comprehension and therefore one should constantly remind oneself of the three characteristics. So first the labeling and then a short contemplation of the 3 characteristics? How are you guys doing mindfulness in buddhist terms? Thanks in advance With metta