Present Perfect Continuous

• The present perfect continuous tense is used when an action started in the past and has not finished yet

• It helps me to refer to a grammar book every so often to remind myself of the "rules".  

• The present perfect continuous refers to an unspecified time between 'before now' and 'now'. The speaker is thinking about something that started but perhaps did not finish in that period of time. He/she is interested in the process as well as the result, and this process may still be going on, or may have just finished.

• Here's another good definition on the English use of the present perfect (from this website):
  
  
  1: To say how long for unfinished actions which started in the past and continue to the present. We often use this with for and since. 
  • I've been living in London for two years.
  • She's been working here since 2004.
  • We've been waiting for the bus for hours.
  2: Actions which have just stopped (though the whole action can be unfinished) and have a result, which we can often see, hear, or feel, in the present (focus on action). 
  • I'm so tired, I've been studying.
  • I've been running, so I'm really hot.
  • It's been raining, the pavement is wet.
  • I've been reading your book, it's very good.