Words And Actions That Lead to To Loss Of Faith

Any Muslim can become an unbeliever by uttering only one word of disbelief — kufr. Doubt in one of the provisions of our religion, mockery and desecration of Holy Quran, angels or one of the prophets are signs of unbelief. One who uses words leading to kufr may lose faith and not even know it. What words and actions lead to loss of faith?