发抖 (fā dǒu) is the general, neutral word for 'to tremble', used for cold, fear, or excitement. 颤抖 (chàn dǒu) is more literary and describes continuous, slight trembling; 哆嗦 (duō suo) is very colloquial, often for shivering from cold or nervousness. The single character 抖 (dǒu) can also mean 'to tremble' but has other meanings like 'to shake something out'.