1. Relationship between past and present

We use the present perfect when:

a) there is​​ a connection​​ between the past and the present:

I​​ have read​​ this book.​​ (So I know it)

b) we give​​ new information:​​ 

 I​​ have broken​​ the vase.​​ (So it is broken)

) to talk about things people​​ have done​​ or​​ experienced​​ and the exact time is not important and the action​​ can be repeated:

 He​​ has travelled​​ to several countries.​​ (Not important when)

2.​​ With adverbials

We use the present perfect with adverbials which show a​​ connection​​ between the past and the present:

already, yet, still, just, so far, up to now, ever, never, recently, since, for, ever, before, etc.

 I​​ have already finished​​ the project.

 Peter​​ has lived​​ in London and New York​​ so far.

 She​​ has just completed​​ her degree.

 Have​​ you​​ ever been​​ to New York?

 I​​ have never eaten​​ a frog.

3. With time reference

We use the present perfect to talk about​​ a period of time​​ which​​ started in the past​​ and​​ continuing into the present​​ (and perhaps beyond).

We often use:​​ ​​ today, this + morning/afternoon/week/year, etc.

 I’ve travelled​​ a lot.​​ (in my life and can do it again)

 I have​​ taken​​ two exams​​ this week. (the week is not finished)

 She​​ has​​ written​​ three emails​​ this morning.​​ (the morning is not finished)

4. In clauses of time and condition

We use the present perfect simple to refer to a​​ future action​​ which will be completed.

 I will send you an email​​ after I have finished​​ my homework.

 Can you​​ give me a ring​​ when you have arrived​​ to the hotel?

 Once you have found​​ your passport, you can travel again.

5. With since, for, how long

We use the present perfect simple to describe how long an activity is if the activity started in the past and​​ continues to the present or into the future.

We use:​​ since, for and how long

 I​​ have lived​​ in Beijing​​ for​​ 6 months.​​ 

 He​​ has worked​​ for Microsoft​​ since​​ 1996.

 How long have​​ you​​ had​​ this car?

6. With superlatives

We can use the present perfect simple​​ with superlatives​​ to say that something we experience is the best/worst, first, etc that has happened to us so far.

 It’s​​ the best​​ cake I​​ have ever eaten.

 It’s​​ the most​​ expensive holiday I​​ have ever had.

 It’s​​ the first time​​ I​​ have been​​ here.

7. For or​​ since?​​ 

We use​​ for​​ to say how long an activity is (a period of time). We use​​ since​​ to say when an activity started.