I'm planning trip to Amsterdam and I would like to know which coffee
shop is the best :-)

Hello lcfat and thank you for your question.

It looks like "Homegrown Fantasy" is one of the best, see:
http://www.coffeeshop.freeuk.com/Database/ShopsA/Homegrown.html

The home page for the directory is here:
"Amsterdam Coffeeshop Directory"
http://www.coffeeshop.freeuk.com/

You might also like to try "Balou"
http://www.hiptravelguide.com/amsterdam/php/reviews-153.html

"Hip Guide to Amsterdam"
http://www.hiptravelguide.com/amsterdam/php/index.php


Thank you for your question, and if you need any clarification of my
answer, do not hesitate to ask before rating my answer.

Very best regards

THX1138

Search strategy included:
"best coffee shops in amsterdam" 
://www.google.com/search?hl=en&lr=&ie=UTF-8&as_qdr=all&q=+%22best+coffee+shops+in+amsterdam%22+&btnG=Search

Thank's for your help :-)

I used to live in Holland and I can tell you that there are two types
of coffee houses in Amsterdam: those that ask you 'Which Menu would
you like?' and the other sort.

The ones with two menus typically had a poster of Bob Marley on the
wall and there was a rather distinctive odour.