Fairies are known for mischief and malice. Most of them would simply commit pranks that are annoying but generally harmless but more sinister are the many deaths and episodes of destruction that were also attributed to fairies.
They were even said to be in league with demons and their auxiliaries, the witches, with whom they share many supersitions.
As a consequence, practical considerations of fairies have normally been advice on averting them. Folktales and legends give more details on the way to deal with faeries and how to protect from their negative influence.