Wah How to use adverbs of frequency.

We use some adverbs to describe how frequently we do an activity.

These are called adverbs of frequency :

100% = always

75%   = often/frequently

50%   = sometimes

25%   = occasionally

5%     = hardly ever, rarely

0%     = never

• The actress always wears expensive jewels.
• The teacher has always been easy to consult with.
• I often go to the gym in the evening.
• They frequently go to the cinema together.
• I sometimes eat vegetables and fruits.
• He sometimes reads the newspaper.
• I occasionally drink alcohol.
• We occasionally have a dinner together.
• He hardly (ever) visit me.
• It hardly (ever) rains in this area.
• Our meeting rarely starts on time.
• I never climb the mountain.
• You will never walk alone :)

Note: We can use hardly to indicate a minimal level of ability of an action.
    I hardly hear you, what was that?
    You have changed so much that I can hardly recognize you.
    I hardly know how to do it.

Where can we put these adverbs in a sentence?

Wah How to use "Once, Twice, Three Times..."

If you want to say how often you do something, You can use...

    one time (once)
    two times (twice)
    three times
    four times
    five times, etc.

       Q: How many times a week do you go to the movies?
       A: I usually go to the movies twice a week. 

       Q: How often do you wash your hair?
       A: I wash my hair three times a week.

       Q: How often do you eat raw fish?
       A: I eat raw fish once a week.

You might hear the word once upon a time.
    According to OED, once upon a time means at some time in the past (used as a conventional opening of a story). 

What about a long time ago?
    It means a long time ago in the past. Now, they could be used interchangeably in some cases, but once upon time could refer to something that happened a few days or a month ago, which is not long time ago, while the other couldn't.