How does a servant become one of Allah's Awliya (saints/devout friends), what is the difference between a righteous man and a Wali, and who is a Wali?

A wali (saint/friend of God) is the pious believer, as confirmed by Allah’s saying: "Unquestionably, [for] the awliya' of Allah, there will be no fear concerning them, nor will they grieve. Those who believed and were fearing of Allah." Wilaya (sainthood/friendship with God) is not restricted to specific individuals; rather, it encompasses all righteous, believing, and pious people. The earth is never devoid of Allah’s awliya, as the Prophet (peace be upon him) said: "A group from my nation will remain manifest upon the truth until the command of Allah comes."