Each parent speaks their own native language to one’s child. For example, the mother, a native Italian speaker, speaks Italian to the children and the father, a native English-speaker, speaks English to the children. This is the most effective approach and is strongly encouraged.
Ideally, both parents need to have at least some ability in the minority language to make this a viable option over the long-term. Otherwise, this approach can be complex from a practical standpoint (for example, if the mother speaks Italian to the children but the father can’t understand what she’s saying and therefore can’t participate in the conversation without translation).
Fill your days with songs, bedtime stories, chitchat and conversation in both languages, including time with native speakers as much as possible. This can mean an extra demand on your time and energy.
Use books, audiotapes and CDs, videotapes and DVDs, and bilingual or immersion language programs.
Recognize your children’s emotional needs.
Children should not be forced into bilingualism.
Children should not be asked to “show off.” This can embarrass children and can make them feel different, casting a lingering negative pall on their bilingualism.
Do not make drastic abrupt changes in your child’s language environment, such as suddenly speaking only a language that you have not used with your child before. This can be quite stressful, especially if the shock comes from the primary caregiver or parent. Introduce a new language with a gradual steady change instead.
Choose a pattern and go with it.
Parents need this discipline/structure even more than the children.
Children can learn two or more languages even in chaos, but a reasonable amount of consistency makes their job much easier.
Once children learn the pattern, they are often disturbed if a parent breaks it.
The more you make bilingualism seem like a natural and unremarkable part of family life, the more likely your children are to enjoy being bilingual.
Speak to your child in a way that feels natural and that you can sustain for a long period of time.
Try to be as consistent as possible in the way that you expose your child to the two languages.
Bilingual children may be slower than monolingual children to acquire either language, but once they reach a high degree of competency in both, they have significant intellectual advantages.
Time lags in the acquisition of reading and writing skills turn out to be temporary.
Bilinguals quickly catch up and (statistically) surpass monolingual peers in a variety of domains.
Cognitive and developmental advantages of bilingualism, again, supported by decades of research, include but are not limited to:
Verbal intelligence and auditory discrimination.
Plasticity in thinking.
The ability to switch quickly between different paradigms and cultural contexts.
Facility in handling novel situations and adopting original approaches to problem solving.
Creativity — “thinking out of the box.”
The ability to ignore irrelevant or misleading information and, thus, navigate complex situations.
Bilinguals are also better at dealing with abstract information. There may be a tacit realization of arbitrary nature of the words that signify the same objects in (their) different languages. On this theme, bilinguals (age-appropriately, of course) are able to reflect on their own experience as language users. They become fearless meta-linguists. Unlike monolinguals—who (linguistically speaking) are like fish that do not realize they swim in water—bilinguals know, first hand, the differences and commonalities that exist between languages. Their knowledge of the grammatical rules of their own languages is powerfully consolidated and their potential to acquire a third or fourth language is enhanced.
As bilinguals grow into adulthood, they are able to recognize and appreciate the fact that a given language always carries with it particular ways of thinking and certain, inextricable cultural assumptions. This is, perhaps, the most important gift of all… Bilingual students obtain the hard-to-pin-down but priceless, attribute of increased inter- and intra-cultural understanding. The significance of cross-cultural communication for young people who aspire to making a difference in their world is not obscure.
Learn more about the bilingual brain by downloading the articles “Structural plasticity in the bilingual brain” and "Second-Language Acquisition and Bilingualism at an Early Age and the Impact on Early Cognitive Development" (PDF).