Where to Place Adverbs of Frequency

Adverbs of frequency tell us how often something happens/is the case, happened/was the case, will happen/will be the case, etc.

There are lots of them. Here are some examples:

always - Peter is always getting into trouble.
usually - They usually get their work done on time.
frequently - My sister frequently goes shopping in Seattle.
rarely - They rarely ask questions about the homework.

The most common adverbs of frequency in English in order from most often to least often:

always - He always does his homework.
usually - They usually complete the work on time.
often - I often watch movies online.
sometimes - Jack sometimes comes over for dinner.
occasionally - She occasionally asks a question.
rarely - They rarely have any homework.
never - I never complain at work. 

Where do adverbs of frequency come in the sentence?

Word order can be confusing with adverbs of frequency. Here are different rules for placement in sentences.

1. If the sentence has one verb in it (e.g. no auxiliary verb) we usually put the adverb in the middle of the sentence, i.e. after the subject and before the verb:

subject / adverb / verb / predicate

Tom usually goes to work by car.
Mary often asks me for help. 

2. The adverb usually comes after the verb "be":

subject / verb / adverb / predicate

Tom is often late.
Anne isn't usually sick.
Peter isn't always right.

This is not the case if we put the adverb at the beginning or end of the sentence for emphasis.

This rule also does not apply to short answers:

Is she usually on time?
Tell her not to be late.
Yes, she usually is.
She never is.

The rule is broken in other cases too, e.g.

Conversation 1

Speaker A: What are you doing here? Shouldn't you be at school?

Speaker B: I normally am at school at this time, but my teacher is ill. 

Conversation 2

Speaker A: You're late again!

Speaker B: usually am late on Mondays because the traffic is so bad.

Conversation 3

Speaker A: Tom is late again!

Speaker B: Tom usually is late. 

3. If the sentence has more than one verb in it (e.g. auxiliary verb) we usually put the adverb after the first part of the verb:

subject / helping verb or modal / adverb / main verb / predicate

I can never remember his name.
Anne doesn't usually smoke.
The children have often complained about the playground facilities.

Exception:

In sentences with "have to" the adverb is in position A:

subject / adverb / have to / main verb / predicate

We often have to wait for the bus.
She never has to do any housework.
They sometimes have to stay after class. 

4. For emphasis we can put the adverb at the beginning or end of the sentence.

At the end is unusual - we usually only put it there when we have forgotten to put it in earlier.

adverb / subject / main verb / predicate

Sometimes we go to school by bus.
Often he waits for her after class.
Usually Peter arrives early for work.

OR

subject / main verb / predicate / adverb

We go to school by bus sometimes.
They like to watch TV often.
Jennifer busy a new car rarely.

Exceptions to the Rule:

"Always" can't go at the beginning or end of the sentence.

"Never", "seldom", "rarely" can't go at the end of a sentence. They only go at the beginning of a sentence in "polemic statements". Then they have to be followed by the word order for questions:

Never has there been a better time to overcome our differences.
Rarely do we have an opportunity like this.
Seldom had the orchestra given a worse performance. 

5. When using adverbs of frequency in the question form, put the adverb before the main verb.

auxiliary verb / subject / adverb / main verb / predicate

Do you often go to the cinema?
Did he sometimes leave the classroom?
Do they usually come late to class?

Exceptions:

"Never", "seldom", "rarely" and other adverbs of frequency with a negative sense are not usually used in the question form.

6. When using adverbs of frequency in the negative form, put the adverb before the main verb.

subject / helping verb / adverb / main verb / predicate

They don't often go to the cinema.
She doesn't usually wait for an answer.
Peter doesn't normally want to come with us. 

Exceptions:

"Never", "seldom", "rarely" and other adverbs of frequency with a negative sense are not usually used in the negative form.

Source: http://esl.about.com/od/intermediate-adverb-adjective/fl/Adverbs-of-Frequency-Sentence-Placement.htm?utm_content=20160705&utm_medium=email&utm_source=exp_nl&utm_campaign=list_esl&utm_term=list_esl