Theorie:

Study the information about the 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  constantly usually  often sometimes  rarely  never
 habitually normally frequently occasionally infrequently     
 chiefly mostly repeatedly  sporadically seldom  
 predominantly  generally   intermittently    
 typically commonly     
 continuously largely    
  regularly     
 
Where should they be put in a sentence?
  
1. If the sentence contains one verb (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:  
  
Tom usually goes to work by car.
  
2. The adverb is usually put after the verb "be":  
  
Tom is often late.
  
3. This is not the case if we put the adverb at the beginning or end of the sentence for emphasis.
 
- Is she usually on time?
-Yes, usually she is.
  
4. If the sentence has more than one verb in it (e.g. auxiliary verb) we usually put the adverb after the first verb:  
  
I can never remember his name.
  
In the sentence with 'have to' we usually put the adverb before the first verb.
 
We often have to wait for the bus.
  
5. For emphasis we can put the adverb at the beginning or end of the sentence.   
 
Sometimes we go to school by bus.
We go to school by bus sometimes.
  
Exceptions:
 
1) "Always" can't go at the beginning or end of the sentence.
  
2) "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.
  
6. When using adverbs of frequency in the question form, put the adverb before the main verb.
 
Do you often go to the cinema?
  
Exceptions: "Never", "seldom", "rarely" and other adverbs of frequency with a negative sense are usually not used in the question form.
  
7. When using adverbs of frequency in the negative form, put the adverb before the main verb.
 
They don't often go to the park.
 
Exceptions: "Never", "seldom", "rarely" and other adverbs of frequency with a negative sense are not used with a negation.
 
Quellen:
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