Rule 1: 1. كَانَ with the imperfect: the habitual past
كَانَ + imperfect describes a repeated or continuous action in the past, used to, would. Once the frame is set, following verbs may stay in the plain imperfect, joined by وَ or فَـ, and still refer to the past. كَانَ كَثِيرًا مَا + imperfect means it often happened that; قَلَّمَا + verb means seldom. مَا زَالَ + imperfect still links the past to the present of the narrator.
كُنْتُ أَنَامُ عَلَى حَصِيرٍ فِي زَاوِيَةِ الْغُرْفَةِ.
kuntu anāmu ʿalā ḥaṣīrin fī zāwiyati l-ghurfati.
I used to sleep on a mat in the corner of the room.
كَانَتْ أُمِّي تُطْفِئُ السِّرَاجَ فَيَمْتَلِئُ الْبَيْتُ بِالْأَصْوَاتِ.
kānat ummī tuṭfiʾu s-sirāja fa-yamtaliʾu l-baytu bi-l-aṣwāti.
My mother would put out the lamp, and the house would fill with sounds.
يَمْتَلِئُ is still past: the frame كَانَتْ governs it.
كَانَ كَثِيرًا مَا يَطُولُ اللَّيْلُ.
kāna kathīran mā yaṭūlu l-laylu.
The night was often long.
Literally 'it was much that the night grew long'.
قَلَّمَا اسْتَعْمَلَ الشَّيْخُ عَصَاهُ.
qallamā staʿmala sh-shaykhu ʿaṣāhu.
The shaykh seldom used his stick.
مَا زِلْتُ أَذْكُرُ رَائِحَةَ ذٰلِكَ الْحِبْرِ.
mā ziltu adhkuru rāʾiḥata dhālika l-ḥibri.
I still remember the smell of that ink.