ن is produced with the part near the tongue tip against the upper gums. Its contact lies slightly forward of ل, although both use the front tongue region.
Listen to the onset of nun in نَعْبُدُ. Omitting the tongue closure or letting it flow like lam does not produce a proper nun.
Nun also has ghunnah, a nasal sound associated with another region. Distinguish the tongue articulation of nun from the nasal resonance of ghunnah, discussed at point 17.