the present perfect

(British English and
American English have different rules for the use of the present
perfect. The comments being made here and the exercises state the
correct grammar for British English. However, in American English, it is
often considered acceptable to use the past simple in some of these
examples.)

We use the present perfect when we want to look back from the present to the past.

We can use it to look back on the recent past.

• 
  I've broken my watch.
  
• 
  She's taken my copy.
  
• 
  They have cancelled the meeting.
  
• 
  The company has doubled its turnover.
  

Often when we look back
on the recent past we use the words 'just' 'already' or the word 'yet'
(in negatives and questions only).

• 
  I've just finished.
  
• 
  She's just arrived.
  
• 
  We've already spoken about that.
  
• 
  They've already met.
  
• 
  I haven't finished yet.
  
• 
  They don't know yet.
  
• 
  Have you spoken to him yet?
  
• 
  Has he got back to you yet?
  

We can also use it to look back on the more distant past.

• 
  I've been to Singapore a lot over the years.
  
• 
  He's done this type of project several times before.
  
• 
  They've talked about it in the past.
  
• 
  We've spoken to them on several occasions over the years.
  

Often when we look back on the more distant past we use the words 'ever' (in questions) and 'never'.

• 
  Have you ever been to Indonesia?
  
• 
  Has he ever spoken to you about the problem?
  
• 
  I've never met him.
  
• 
  We've never considered investing in Canada.