是often to do，often后面不加doing;often 表示一般现在,所以要用do。often作为副词，基本含义为“经常”、“往往”、“常常”、“时常”、“大多”，常放于行为动词之前，特殊动词、助动词、情态动词及动词be之后，也可放在句末表示强调。

often

adv.时常;常常;往往;大多;

比较级:more often;最高级:most often

often作为副词，意为经常;往往;常常;时常;大多。例句有:

1、I've often wondered what happened to him.

我时常纳闷他出了什么事。

2、People are often afraid of things they don't understand.

人往往对自己不懂的东西感到恐惧。

3、They often spent Christmas at Prescott Hill...

他们经常在普雷斯科特山过圣诞节。

4、How often do you brush your teeth?...

你多久刷一次牙?

5、She's going to come back every so often...

她会偶尔回来的。

6、The disease often goes/ remains undetected for many years.

这种疾病经常潜伏多年而不被察觉。

7、People often give very different accounts of the same event.

人们常常对同一件事的叙述大为不同。

8、Stress is often a factor in the development of long-term sickness.

心理压力常常是形成长期病的一个因素。

9、Talking to others can often help to put your own problems into perspective.

跟别人谈谈往往有助于正确处置自己的问题。

10、It is often helpful for teachers to shadow managers in industry.

教师跟随业界的管理人员实地学习，常常会很有收获。