Myths

Bilingual families are an anomaly.
It may seem this way in many areas of the United States. However, this is not the case worldwide. For example, half of Europe is already multilingual — 45% of European Union citizens can take part in a conversation in a language other than their mother tongue.† In many countries it is quite normal for people to be able to use two or even three languages.

Learning two languages simultaneously causes a speech delay and confuses children.
According to ASHA, children all over the world learn more than one language without developing speech or language problems. Bilingual children develop language skills just as other children do. Certainly, it is important to be aware of normal language development. According to ASHA, there are expected language behaviors for each age, but children develop at different rates. Look for continuous language growth. Should you have concerns, consult a speech-language pathologist.

People often ask me if my daughter was delayed in speaking since that seems to be a common assumption that speaking more than one language to a child from infancy will confuse them and cause delayed speaking. My daughter was incredibly verbal in both languages from one year on and talked very early in complete sentences.
— Mother of bilingual 2 1/2-year old (Spanish)

In fact, there may actually be developmental benefits to being bilingual. Bilingualism has been shown to foster classification skills, concept formation, analogical reasoning, visual-spatial skills, creativity, and other positive cognitive gains.††

Speaking a second language at home has more benefits than disadvantages. For a bilingual person, it's easier to learn a third language and remember that language even if not used often. It's like the brain has learned the trick to learn 2 different languages so it can apply that trick to a third. While I don't use my French, I can remember it when I hear it and am able to respond. I have schoolmates that even though we learned French at the same time (and they were better at it) now can't remember it at all. We attributed to the fact that I constantly speak a second language, while they only speak one.
— Adult raised in bilingual home (Spanish)

There's a right way and a wrong way to handle multiple languages in a family.
Various approaches can work, but it takes dedication and planning on the part of the parents in order to provide a rich and varied bilingual environment for children — one that includes books, songs, stories, and exposure to the second language culture and family.

In order to raise bilingual children successfully, both parents have to be willing to do it and supportive of each other. . . we should be teaching the children not just the language, but the culture as well. After all, language is an integral part of the culture. Without culture, language will be very dry.
— Mother of bilingual 15-year old and 13-year old (Mandarin Chinese)

You have to be "perfect" in both languages to be bilingual.
What does it mean to be bilingual? Bilingual is defined as the ability to use two languages with equal or nearly equal fluency. But raising bilingual children means different things to different families. Consider what it means to you. Ability to understand the second language? Speak it? Read and write it?

I think I expected they would just be bilingual and have learned that it takes work and planning. . . Having spent some time studying the language, I just want them to be able to get something out of their mother's culture and know that part of their family in a way I cannot as a functional illiterate with limited conversation skills.
— Father of bilingual 11-year old and 7-year old (Japanese)

† According to EUROPA, the European Union's portal site.
†† According to Ellen Bialystok, "Language Processing in Bilingual Children," 1991. Bialystok is a psychology professor specializing in bilingualism and its effect on language/child cognitive development.