Frequency Adverbs

Frequency adverbs can be placed at various points in the sentence.

Adverbs of frequency go before the main verb:
I always come to work on time.

Adverbs of frequency go after "be":
They are never pleased to see me.

Expressions of frequency (every day, twice a week, once a month etc) usually go at the end of a sentence:
I have English lessons every day.

The most common frequency adverbs in English are:

The percentages here are rough estimates only.

To say how often something happens, you can use a number or 'several' or 'many', followed by 'times:
Once a week/month/year
Twice a year/day
several times a year
We can also use 'every' + period of time:
every morning
every day
every Tuesday
every week
every month

A day of the week with 's' at the end (for example 'on Tuesdays') means the same as 'every Tuesday':
I take a dance class on Wednesdays.
I relax on Saturdays.

taken from: 

http://languagelearningbase.com/86243/a2-grammar-adverbs-and-expressions-of-frequency