Doubled mim and doubled nun: ghunnah is required.
Unvowelled mim:
1. Before م — labial assimilation with ghunnah.
2. Before ب — labial concealment with ghunnah.
3. Before other letters — labial clarity, especially before fa and waw.
Unvowelled nun / tanwin:
1. ء ه ع ح غ خ — throat clarity.
2. ي ن م و — assimilation with ghunnah; mind the word boundary.
3. ل ر — assimilation without ghunnah.
4. ب — conversion with ghunnah.
5. ت ث ج د ذ ز س ش ص ض ط ظ ف ق ك — true concealment.
Exception: «دُنْيَا، بُنْيَان، قِنْوَان، صِنْوَان» preserve clear nun. After understanding the rules, repeat the actual sounds and seek correction by a qualified reciter. The next unit covers alif, waw and ya.