Rule 1: 1. كَانَ يَفْعَلُ for a past habit: 'used to', 'would'
Put the perfect of كَانَ before the imperfect indicative of the main verb. Both verbs agree with the subject in person, gender and number: كَانَتْ تَقْرَأُ she used to read, كُنَّا نَقْرَأُ we used to read, كَانُوا يَقْرَؤُونَ they used to read. The imperfect keeps its indicative ending; nothing is inserted between the two verbs except, if you wish, the subject itself: كَانَ أَبِي يَقْرَأُ my father used to read. Expressions of frequency, كُلَّ يَوْمٍ, دَائِمًا, مَرَّتَيْنِ فِي الْأُسْبُوعِ, confirm the habitual meaning.
كَانَ جَدِّي يَأْكُلُ الْفُطُورَ فِي الْحَوْشِ كُلَّ صَبَاحٍ.
kāna jaddī yaʾkulu l-fuṭūra fi l-ḥawshi kulla ṣabāḥin
My grandfather used to eat breakfast in the courtyard every morning.
كَانَتْ أُمِّي تَخْبِزُ الْخُبْزَ فِي الْفُرْنِ مَرَّتَيْنِ فِي الْأُسْبُوعِ.
kānat ummī takhbizu l-khubza fi l-furni marratayni fi l-usbūʿi
My mother used to bake bread in the oven twice a week.
Both verbs are feminine.
كُنَّا نَصْعَدُ إِلَى السَّطْحِ وَنَنَامُ هُنَاكَ فِي الصَّيْفِ.
kunnā naṣʿadu ila s-saṭḥi wa-nanāmu hunāka fi ṣ-ṣayfi
We used to go up to the roof and sleep there in summer.
One كَانَ serves two imperfects joined by وَ.
كَانَ الْجِيرَانُ يَأْخُذُونَ الْمَاءَ مِنْ بِئْرِنَا.
kāna l-jīrānu yaʾkhudhūna l-māʾa min biʾrinā
The neighbours used to take water from our well.
كَانَ stays singular before the noun subject; the imperfect is plural.
كُنْتِ تَسْأَلِينَ عَنْ كُلِّ شَيْءٍ وَأَنْتِ صَغِيرَةٌ.
kunti tasʾalīna ʿan kulli shayʾin wa-anti ṣaghīratun
You (f.) used to ask about everything when you were little.