I have four year old twins (See my avatar), they currently can communicate in Mandarin, English and Cantonese (Cantonese being their weakest language).

The way it is handled in my home is that I communicate with them in English, my wife in Mandarin and the mother-in-law & maid talk to them in Cantonese. 

One of the important things to do is make sure that they have lots of material (Books, DVDs, Computer games, etc...) that are in English (or whatever your native language happens to be).  Kids learn really fast from these things.

Also, story time is very, very important.  The more they hear you speak, the quicker they will pick up the language.

And finally, make sure the school you send them to is really capable of teaching them the languages of your choice.

Hope that helps a little.  Raising kids here is a real challenge, but it can be really fun too.

it is all about the lips make them look at the lip they will learn 

i did not say tongue becuase the lips are more important but the tongue helps a lot to

To answer HappyExPat
the lips and the tongue the people who learn language the fastest know this consciously or unconsciously.  Language means nothing without the ability to speak. Have you ever met someone with a speech disorder or someone who is deaf they always teach them to look at the lips and the tongue how do you think people can read lips? That is why people go to classes for years and study abroad?

My thought on new language learning is that the more you use it, the more you hear it (and of course, practice it), the faster you will learn a new language. 

But I never heard that you can learn a new language by looking at someone's lips.  Could you please elaborate a little further on your comment ? 

Thanks

PS:  I have 5 kids, 4 boys and one girl.  They all speak at least three different languages, a couple speak even one or two more.  And It was done just as ExPat John said, different family members used always one language to talk to each of them.  For example, my oldest son now is fuent in Spanish, English, French, Sweedish and German, and knows some Italian too.

I knew one guy that raised by giving them a name in each language he wanted them to learn.  And when he used that name, that's the only language that was allowed to be used for the conversation.

With my 2 years-old son, my wife communicates with him in Chinese and I communicate with him in French, and on some occasion I sing some Italian songs to him.

He however gets to hear English on a daily basis as my wife and I speak in English together, and when I am with other mothers we also use English rather than any other languages.

Since none of us are English mother tongue, it's not a good idea to introduce English by communicating with him. I would not advise non English-native speaker parents to do that with their children. A person may have a good command of English as a second language and expresses himself/herself very well, but a language doesn't only carry words, it also carries emotions, tones and a non-native speaker is hardly able to express these kind of feelings naturally.

On a second point, I would slightly disagree on learning English with DVD, computer games with children, because they don't actually learn. It's proven that children watching TV lose a great deal of concentration and their learning process slows down as the child cannot interact with the TV or the characters on the TV. His brain is in a passive mode, not in active one. Besides having parents of a different mother tongue, the most practical way to introduce another language to a child is through activities in that foreign language (dancing, singing, playing) with a native speaker as the child is always active and ready to learn things.

I often goes out with a Russian mother, we speak in English together, however, she speaks in Russian to my child and I speak in French to hers. Then they both catch some words and just repeat them.

Monolingualism is a minority in this world. Africa, Europe, large parts of Asia, the Americas etc, are bascially all bi- or multi-lingual. In China, most people have at least 2 languages to some good proficiency, and in the south, many children are getting 'fluency' in 4 languages - their hometown language, Putonghua, Guandonghua, and because of the educational requirements, English. Most Europeans have at least 2 languages, usually more (even if because those languages are related).

In Africa, most people have at least 2 languages, usually 3, and often 4 (depending on level of education). Again, they have their hometown langauge, plus large parts of Africa have adopted Swahili as the official language, alongside either English or French (whcih have become official languages due to colonisation) and they are used as lingua franca's, and are often the language of tertiary education, as well as government business. Due to the influence of Islam in many countries, they may also have some Arabic (though perhaps not at conversational ability - unless in the north of Africa - Algeria, Tunisia, Morocco, etc).

For most of the above, they do NOT have access to a 'native' speaker.

If you want to have your children multi-lingual, just introduce it to them early on, and try to use that language/s regularly with them. Perhaps, choose 1 day a week for each language you want - NOT including the local language. They'll get enough of that from everyone else around them! (and, of course, they'll hear you speaking it in those contexts)

Be aware, although most people on the planet are able to speak a multitude of languages, the level of fluency is different, and there will always be one language that is better than another - in each particular environment! Eg, a German may have perfect German and Dutch for social environments, but their English will be much better than either in, say, IT fields... just the nature of what is used when. Also, if German is used to speak with most family members, and Dutch is used to speak to their grand-parents, then you'll find that their Dutch would be more formal than their German, and they'd have difficulties (or sound not so native) in Dutch when speaking to others.

Tv, DVD, etc are great!

So to is the latest version of Rosetta Stone! If I had kids, that's what they'd be looking at !!! (while I was learning a new language as well )

My dad learned English from his parents, neither of whom spoke English as a first language.  My Grandmother was German (Prussian she would correct) and my Grandfather was from Quebec. You can guess what their first languages were. Anyway, as Grandma did not speak French and Grandpa did not speak German, they used English as the common language and spoke it to their kids (who had typical Mid-Western accents).

I will add some comments about what Shining_brow said.

Actually, I'm sorry to contradict you but you don't back up anything. Your comment is essentially describing general situation, but not really pertinent to a kid's learning situation like it was suggested in the original question.

A language is used to communicate feelings, ideas, opinions, information, instruction, etc.  When children, especially young ones, communicate or learn to communicate in a language, they need an interaction with the person they speak to. When my child speaks to me in Chinese, I answer in French, not because I cannot answer to his questions or his words in Chinese, but because, despite my good knowledge of Chinese, I cannot carry out the underlying essence or aspects that go together with the Chinese language.

You like to emphasize that people can get "fluent" in four languages, well I have some doubts about it. I work as a translator, and if before I could consider myself "fluent" in three foreign languages, I started to realize that even in my mother tongue, I cannot pretend to be that "fluent". Certainly, if "fluency" is related to just ordering food in a restaurant in three different languages, then we are all fluent after one week abroad. But give you three tests, do it from your mother tongue into a foreign language : 1) cook something, at the same time, translate the whole process into the foreign language from A to Z, translate all the kitchen/cookingwares that you use, all the ingredients that you use, all the actions that you do (simmer, boil, fry, grate, etc); 2) take a cab, at the same time, describe all the components of this cab in a foreign language (at least 20 parts), 3) go through your apartment, describe all the items in your living room (at least 50 items). What does it say about our "fluency" in a foreign language. You'll then be able to make one day per week where you speak only a foreign language to a kid.....if you cannot pass one of this test, I doubt it....that's why I don't want to teach him English for instance by myself, but will rely on a native speaker to do it.

It's true that in China and in many part of the world, people are bi/multilingual, it doesn't necessary imply that they are "fluent" in their second, third or fourth language. They can certainly communicate in those different languages or dialects pretty well on a daily basis, but if they have to go deeper in describing things, then they may hurt a wall of unknown words. And what you say "the level of fluency is different, and there will always be one language that is better than another - in each particular environment!", just tend to prove that there isn't really a fluency in all the foreign languages that one may speak, but a more or less better understanding of it.

Again, you learn a language because of the people who communicate with you in a specific language, in the case of a family : the father speaks cantonese, you get to hear, learn, answer in Cantonese; the mother speaks Mandarin, you get to hear, learn, answer in mandarin; the ayi speaks a Shandong dialect, you get to hear, learn, answer in that Shandong dialect; at school, the teachers speak English, you get to hear, learn, answer in English. You will certainly be able to listen and speak in those languages and dialects later on, but I have some doubts that all the learned languages would remain so fluent.

You said that you haven't any kid, then it's difficult for you to judge the learning situation for a young kid. They are effectively like sponge, able to catch everything....but they also don't understand (especially young ones) the difference between what is shown on TV and the reality itself. I observed my child when he is sometimes watching TV, he doesn't even blink one eye for a long time and he is totally immerse in what he is watching. 

For a child, to learn a language, he is needs to hear it from a native speaker that's how he can keep not only the words, but also the pitch, the intonation, the underlying meaning that goes with them. Then, if you want him to watch a DVD to learn a foreign language, you need to be by his side, and discover the DVD with him. Communicating what the DVD says, playing what it's played on the DVD, singing what is sung on the DVD, etc. That's how you can try to teach a foreign language to your child.  

I'm Tanzanian, I learned three languages simultaneously while growing up... I speak Swahili, English and my parent's local dialect (which they spoke in the village,I was born in the city but I picked it up from them).

For me it feels like it just happened naturally but the thing I speak better English than my parents and so everything was calculated to ensure that I grow up speaking a foreign language. What they did was, they got me a bunch of VHS (back then) tapes which I would watch religiously. They were English learning materials, like Sangoku said (I dont think I could have put it any better)..singing the songs with your kids is the most efficient way. I really enjoyed that and my parents would also learn English in the process so it was good experience for all of us. My favorite childhood memories include putting on a show for my parents as I "performed" my favorite songs and they would video tape me.
My advice would be to make it an enjoyable family affair, watch the DVDs together gradually advancing from the most basic level to more complicated ones like a full-on cartoon movie.
I don't think I've said anything you haven't heard before but I hope it helps good luck
 

The two most widely recognised and used systems for teaching young children more than one language are 'One Parent One Language' (OPOL) and 'Minority Language at Home' (MLH). Firstly though educational psychologist have proven that children under about the age of 6 don't 'learn' languages as they have to when they're older, they 'absorb' them, there is something in the brain that 'switches off' after about this age, so both systems are dependent on the children absorbing the languages before this age.

OPOL is best used when you want the child to learn a language different to the native language of the country in which you / they are living. e.g. My situation, I am English, my wife is Chinese we are living in China, at home or whenever my daughter is within earshot, I will only speak English, if she speaks any Chinese I pretend (pretty easy with my level of Chinese) I don't understand, already she is proficient in the basics of English and she is only 2 years old.

MLH, is when both parents speak the local native language most of the time but when in the home everyone only speaks whatever the 'other' language is. e.g. when we go back to the UK, hopefully by then (9 years time) my Chinese will be proficient, when at home we will only speak Chinese.

The problems with both systems are discipline and sticking to your guns, there will come a time when the child will 'rebel' against the language being learned esp if he / she doesn't use it amongst his / her peers e.g. at school, the adult minority speaker has to be harsh and disciplined and not give in to the child.