What is the way to gain the guardianship of Allah, the Mighty and Majestic? And can a sinner be among His Awliya' (saints/devout servants)? And what are the characteristics of Allah's Awliya', and how can one attain them in detail?

The Awliya' (friends) of Allah are every believing and pious person, as the Holy Quran clarifies in the verse: "Unquestionably, [for] the allies of Allah there will be no fear concerning them, nor will they grieve. Those who believed and used to fear Allah." They are divided into the foremost (preceding ones) who are the 'Muqarrabun' (those drawn near), and the 'Muqtasidun' (moderate ones) who are the companions of the right. The Wilayah (friendship/sainthood) of Allah is attained through faith, piety, performing the obligatory acts, avoiding prohibitions, and increasing in supererogatory acts elevates the degree of Wilayah. It is not a condition for a Wali of Allah to be infallible from error or sins; rather, he may fall into them, but he is quick to return and repent.

Everything that falls under faith and piety, including performing commanded acts and abandoning forbidden ones, is among their characteristics.