often 这个词一般用于动词之前,be 和助动词之后,举个例子,比方说：I often go to the library.(此句中,often 放于动词前.）
I do often go there.(此句中,often 放于助动词 do 后,do在这里是起强调作用.)
Old houses are often damp.译文：旧房大都潮湿 （此句中,often 放于be动词后.）（这句话来自牛津字典
也有放于句末的用法,我给你几个例子：
He writes to me often.他常常给我写信.
We've been there quite often.我们经常在那里.
如果遇到 very often的话,其实放中间与放句末都是可以的,它用于句末来加强语气.但是,放句中也可以的,比如：
It very often rains here in April.这儿四月份常下雨.