A Local "Devotion" Grows Up Around Your Memory
During your life, if you were an especially holy person, you probably got noticed in your locale or perhaps even by the world at large, especially if you were a "public" religious person, like a sister (like Mother Teresa), brother (like Francis of Assisi), priest (like Padre Pio), a founder of a religious order (like Dominic) or pope (like John Paul II). In general, it's harder for laypeople to become saints not because they're less holy, but because the process takes a lot of time and persistence, which usually only religious orders (e.g., the Franciscans, Jesuits, Dominicans, etc.) or dioceses have to spare. You could be the holiest mother or father in the world, but your children may not know all the ins and outs of the canonization process. But don't give up if you're not a professionally religious person: the Vatican is trying hard to identify those holy lay people worthy of sainthood, and they've canonized quite a few lately.
Anyway, people who knew you will naturally start praying to you for help and trying to emulate you. And this "local devotion" can't be faked: the Vatican recently put into effect new rules to prevent any religious congregation or diocese from claiming that people have a real devotion to you, if they really don't.
