Find a teacher. Contact the city of Montreal's referral service for assistance in choosing a language school or tutor. There are many teachers and classes available in the city so you should be able to find a program that is right for you.
Immerse yourself in Dutch settings. Although the Dutch population in Montreal has dwindled since the mid-1980s, there are still organizations like the Canadian Association for the Advancement of Netherlandic Studies that encourage the study of the Dutch language.
Join the Montreal Dutch Conversation Group even if you don't speak much yet. Listen and practice what you do know. Most people are happy to help someone who shows an interest in their language and culture.
Visit the Bibliothèque Interculturelle. This library opened to offer language courses and material for language learning and you can find useful resources there.