How to teach the differences between Past Simple and Present Perfect

Good evening everyone,
How to explain in an efficient way the difference between Simple Past and Present Perfect ?
example :
The Chinese government has challenged the figure, but the trend is unmistakable.
The Chinese government has dealt with the problem for many years .
I have smoked today / I have smoked for 20 years.

OBS: We know that the past simple refers to : completed actions, habits, states

and the present perfect refers to : recent events, without a definite time given/indefinite events which may have an obvious result in the present.

so the question is : what´s the best way to make it clear for the students.

tks.
looking forward to hearing from you
alexandre