PRESENT PERFECT

The present perfect can be used ...

- to describe an action that began in the past and is still going on
now. It is not yet finished.

She's had three cups of coffee today. (She may have more.)
This year has been busy. (The year is not over.)

- to describe a past action or event when it's not important to know
exactly when it happened.

I've forgotten your name. (I don't know it now.)
She's lost her handbag. (She doesn't have it now.)

- to say how many times you have done something.

This is my favorite film. I've seen it three times.
Jane has been to Australia twice.

- to talk about actions and events with time indicators relating to
the present.

Jack has never ridden a horse. (up to now)
Have you ever smoked a cigar? (in your life)
I haven't smoked since 1989. (I hope never to smoke again.)
Sharon has ridden a horse, but she hasn't ridden for ten years.
Have you checked into the hotel YET?

SIMPLE PAST OR PRESENT PERFECT?

The present perfect can describe WHAT you have done, without reference
to time. The simple past is used if you mention a specific time in the
past WHEN you did it. Compare:

I have been to Jamaica. I went to Jamaica three years ago.
John has done his homework. John did his homework last night.
I've already seen the film. I saw the film Wednesday evening.
She has lived in California. She lived in California in 1991.


"FOR" OR "SINCE?"

Use "for" to talk about duration; a period of time
for three hours, for ten years, for as long as you like, etc...

Use "since" to refer to a specific point of time in the past
since 1957, since the last time I wrote, since I was born, etc...


"HAS BEEN TO" OR "HAS GONE TO?"

"Has been to" means "went there and left."

Ann has been to London. (She went there on June 8 and left June 15.)
Bill has been to the bank. (He's back from the bank now.)

"Has gone to" means "there now or on the way there."

Ann has gone to London. (She's in London now or on her way there.)
Bill has gone to the bank. (That's where he is now.)