用doing开头的应该是动名词作主语。例如
Seeing the film, I moved to tears.
用to do 开头的是不定式作主语,如:
To become a doctor is my dream.
用ed开头的是过去分词作判随状语的。如:
Tied her husband,she went into the kitchen.
to do 表示打算,还未做.目的
To be a good student,he works harder than any other student
doing done 用于非谓语 done 表示完成及被动
doing 表示主动
建议你在百度上查查“非谓语动词的用法”