Miftah Tariq al-Awliya
The Key to the Saintly Path
Ibn Shaykh al-Hazzamiyyin
The Key to the Saintly Path by Ibn Shaykh al-Hazzamiyyin is a primer into the science of tazkiya and sulūk.
In it, he details practical steps that you can apply in your day-to-day endeavors that will help strengthen your spiritual connection with Allāh Almighty. If you are sincere and dedicated, He will eventually make you of His righteous servants.
The videos below provide a similarly succinct explanation for proper understanding and application.