Rule 1: 1. What the imperfect expresses
يَعْمَلُ may mean he works, he is working or he will work. Only the setting decides. In a story told in the perfect, an imperfect verb describes what was going on at the time; in a description of someone's trade it states a habit; with a time word pointing forward it is a future.
يَعْمَلُ أَبِي فِي الْمَصْنَعِ.
yaʿmalu abī fi-l-maṣnaʿi
My father works in the factory.
A habit.
يَخْبِزُ الْخَبَّازُ الْخُبْزَ الْآنَ.
yakhbizu-l-khabbāzu-l-khubza-l-āna
The baker is baking the bread now.
Present, fixed by اَلْآنَ.
يَحْصُدُ الْفَلَّاحُ الْقَمْحَ غَدًا.
yaḥṣudu-l-fallāḥu-l-qamḥa ghadan
The farmer will harvest the wheat tomorrow.
Future, fixed by غَدًا.
نَصْنَعُ الْأَبْوَابَ مِنَ الْخَشَبِ.
naṣnaʿu-l-abwāba mina-l-khashabi
We make the doors out of wood.