Rule 1: 1. أَنْ and لَنْ in a conversation
When people speak about wishes and refusals the subjunctive comes thick and fast. أُرِيدُ أَنْ I want to, أَخَافُ أَنْ I am afraid that, طَلَبَ مِنْهُ أَنْ he asked him to all take the subjunctive. لَنْ answers them with a firm refusal: لَنْ أَذْهَبَ I will not go. The phrase قَبْلَ أَنْ before is also followed by the subjunctive, because the action after before has not yet happened.
أُرِيدُ أَنْ أُسَافِرَ مَعَ خَالِي.
urīdu an usāfira maʿa khālī
I want to travel with my (maternal) uncle.
لَنْ تُسَافِرَ قَبْلَ أَنْ تَكْتُبَ دُرُوسَكَ.
lan tusāfira qabla an taktuba durūsaka
You will not travel before you write your lessons.
Two subjunctives: after لَنْ and after قَبْلَ أَنْ.
طَلَبَ مِنَ السَّائِقِ أَلَّا يَتْرُكَهُمَا فِي الْقَرْيَةِ.
ṭalaba mina s-sāʾiqi allā yatrukahumā fī l-qaryati
He asked the driver not to leave them in the village.