Am I avoiding people? Do I try avoid crowded spaces? Do I still attend mass on Sundays? Do I stay clear from animals? Do I bathe more regularly? Etc.
That rather depends on whether you view the problem in terms of modern criteria or the beliefs of the time.
We know that the Black Death is a level 4 bacterial infection that is highly transmissible by airborne, flea bite and contact means, and is up yo 90% lethal if untreated (by antibiotics). So there is very little a medieval peasant can actually do to protect against it, except perhaps by isolating their communities. The principle of quarantine was understood at the time: it was attempted during the sixth century plague of Justinian, for example.
Italy led the way in the fourteenth century when plague began to spread. Venice, for example, appointed health officials.
It was generally believed, based on the medical literature of Avicenna, that the disease had a miasmic/ bad air origin. (Other theories included hot weather and a planetary conjunction)
Without definite knowledge of what caused the disease, Italian health commissioners fell back on a common theory that the air itself was infected. In their view, the only way to stop the epidemic was to somehow clean the air. “In their pursuit of corruption-free air, commissioners inspected wine, fish, meat, and water supplies; they worried about sewage; they regulated burials, and decreed the destruction of the clothing of the deceased.” These measures may have saved lives by cutting down on secondary sources of infection. But besides burning the clothing of the deceased, they did little to curb the rampant spread of the plague.
Gentile de Foligno wrote a tract on the disease and he and other authors recommended several actions, which were probably well known:-
Flee, or if you’re not able to…
Choose a residence on low ground, free from noxious air, far away from marshy, foetid ground.
Cover up windows with cloth except when a fresh north wind was blowing
Burn aromatic herbs to rectify the air
Sprinkle vinegar and rose water round the house and carry scented pomanders (presumably if wealthy enough), and…
Purge your body using diuretics and laxatives
Bleeding, both to rid the body of noxious substances
Avoid foods which easily putrefy in the stomach
Periods of decent sleep
Interestingly, some medical writers, like Guy de Chauliac, were beginning to notice the extreme contagion of the plague and wrote about it.
I am assuming that popular ideas about protecting oneself were much discussed in medieval society, just like medical rumours spread in modern times.
I recommend “the control of plague in Venice and Northern Italy 1348-1600 by Richard John Palmer (thesis at University of Kent at Canterbury) 1978 available online:-