Adverbs of frequency are used to describe how often you do something. 

When using them, think about the percent of the time you do it. 

Always= 100%

Often/Usually= 75%

Sometimes=50%

Rarely= 25%

Never= 0%

Someone might ask you:

How often do you ________?

or 

Do you ever__________?

...and you can answer using adverbs of frequency. 

Example: 

Phoebe: How often do you wear a helmet when riding your bike?

Yelim: I never wear a helmet!

Yelim: Do you ever go out to eat?

Phoebe: I rarely go out to eat, only once in a while. 

You can use adverbs of frequency in the present tense, for things you do or do not do currently, or you can add the verb "to have" and use them with past tense.  In that case, you are referring to how often you have done something in your whole life. 

Example:

Yelim: Have you ever been to Korea?

Phoebe: No, I have never been to Korea. 

Phoebe: Have you always been such a good student?

Yelim: Yes, I have always been a god student. I am rarely absent and I always do my homework. 

(In this example the past and present tense are both used in the same sentence to answer the question)