To me the most difficult grammatical item was present perfect continuous; in fact I still have difficulties with it now. For example: it has been raining. Does the sentence indicate that the rain just stopped or it is still raining? How about: I’ve been waiting for you. Am I still waiting for you, or I am not waiting now. According to the book, present perfect continuous can indicate two kinds of situations. First of all, it can be used to express that the action has just stopped in a very near past. Secondly, it is used to express the continuation of the action. The book I read does not say that when to use what. I guess it all depending on the different situations, if someone says that: I’ve been doing this for my entire life. Perhaps the speaker is talking about his or her career or some habits. In that case the person would probably still carry on doing the activities. On the other hand if I say: the street is very wet, it has been raining. The rain has just stopped perhaps several minutes ago. The other example I mentioned above: I’ve been waiting for you. If I am talking to the person face to face that means my waiting period has come to an end, he or she eventually appeared. If I am writing a letter or talking to the person over telephone line, then I am trying to tell the other party that I am still waiting. However in the first case: I’ve been waiting for you. If I am asking the confirmation of certain relationship say a marital one. In this case even if I am talking to the person face to face, the implication would still be that I am still waiting for your answer.