Buddhist & Hindu temples
Remove shoes where indicated, dress modestly, and avoid pointing your feet toward statues or altars when seated. Photography is usually fine but check for posted signs at more sacred inner areas.
Mosques
Cover shoulders and knees, and women may be asked to wear a provided robe and headscarf at some mosques. Non-Muslims are generally welcome outside of prayer times.
Churches
Modest dress and quiet behaviour apply as anywhere; most are open to visitors outside of active services.