Raising Bilingual Children: Step-by-Step Guide
When I was growing up, my eighth grade "boyfriend" was Polish. It was a rule in his family that when at home you had to speak Polish, and because of this rule he and his little brothers could speak Polish fluently. I even picked up a few phrases while hanging around their house. This was his family's way of keeping their language alive, and one of the methods written about in Christina Bosemarks' article, Raising Bilingual Children: Step-by-Step Guide.
Christina Bosemark is the founder and director of the Multilingual Children's Association. Bosemark speaks several languages and is raising her daughters to speak 3 different languages.

I believe raising bilingual children is a very remarkable thing for parents to do. Children from bi- or multi-lingual families should be exposed to and taught at least one other language even at their young age.
Learning one or both parents’ native language, for instance, allows children to remain in touch with their parents’ culture and heritage, even though they are living in another country. Thus, should they travel to their parents’ country, they would immediately feel a sense of belongingness and familiarity.
I believe being bilingual also helps a child to have a more “flexible tongue” and a “natural dispostion” to learning other languages as well.