Here is a simple, respectful way to speak or chant when you see a derasar (Jain temple):

• Before entering or as you pass by, greet with a respectful Namaskar (folded hands, slight bow).
• Softly recite the Navkar Mantra (Namokar Mantra), which is the most fundamental prayer in Jainism:

Namo Arihantanam Namo Siddhanam Namo Ayariyanam Namo Uvajjhayanam Namo Loe Savva-sahunam Eso Pancha Namokkaro, Savva-pavappanasano Mangalanam cha Savvesim, Padhamam Havai Mangalam

• If you prefer not to chant aloud, you may recite it mentally and bow in humility (panchang pranam) before the murti.
• You may also offer a short, personal prayer or request for forgiveness and purity (Khamemi Savve Jiva, etc.) as per local tradition.
• Speak softly, keep the mind and speech pure, and avoid loud talk or distractions.

Etiquette to keep in mind:

• Remove shoes, keep cleanliness, and dress modestly.
• Do not touch the idols unless the temple allows and you are properly prepared.
• Maintain silence and walk gently, especially near the garbhagriha.
• Follow the specific maryada of the derasar you are visiting, as rules vary by sangh (Shvetambar, Digambar) and local temple.

You can read more here and