How; in what state or condition; in what manner.
If the question word is used by itself with a noun or pronoun, sā'ingge is used for asking about the state of s.t. and inumey for the means of achieving s.t. If a verb is used in the sentence either one can be used.
How can one light this lamp?
To treat in what manner, to do what.
What did he do to you that you fell? (or How did he make you fall?)
How shall I do it when I tell her? (or What shall I tell her?)