1. Teach at early age, start before 3 yrs old.
2. Teach with fun, start with interesting content follow the kid's age. Start from picture cards, with very simple words. Later with some funny lines from 繞口令, jokes, humor stories, TV series(too many), ...
3. Teach consistently, once a day, like brushing teeth.
4. If the kid asks: I am learning English, why I have to do Chinese? Your answer: show how many figers that you have, if more than one
5. If the kid asks: Other kids don't have to learn Chinese, why me? Your answer: look at yourself in a mirror, you are always Chinese and this is your privilege which can make us as your parents to award you some of your favorite gifts at your birthday and Chinese ny in every year.
6. Teach with new words at certain amount, don't overload, neither underload.
7. Let kids join a Chinese class where kids can have some competitions to satisfy their egos.
8. Old saying: it is the father's mistake if he fail to teach his kid. Someone in the family has to take the resposibility for about 20min to 30min a day.
9. Who said again: it is the teacher's mistake if one fails to discipline one's students. Trust the kids in ABC, they are too smart to learn Chinese. If they failed due to lacking of interest, you can find some suitable materials for them when you visit China or many websites. On the other hand, most ABC kids only need to learn one time to remember a new word, if they are not bored, not playing any negative attitudes.
10. Being a bilingual kid has a tremendous advantage, from the multiplication table,to novels and literatures, and an easy excess to 5000 years history. Wisdom is a word with many languages, but the summation of both English and Chinese can allow your kids to enjoy their lives in a different level.
How do I know all about these?
My boy is 15, he has enjoyed in learning Chines for last 14 years, for him, this has become his rest time to enjoy everyday for about 30 min. at least. After finish his reading in 三國演義，and other Chinese novels, plus watching many TV series, such as 海爾兄弟，士兵突擊，etc.
How about his English, fyi, his SAT got 2350. As he commented, learning Chinese can help to understand English with some synergy: such as a simple translation: how are you? how old are you? How can you translate them into: 怎麼是你？怎麼老是你？Dear Mr. YZQ, you can hear his giggling now.