My entire family is bilingual. We do it by speaking both Spanish and English around the kids from birth. The bad part is they start speaking much later (my sister started pre-k without speaking) but once they've gotten the hang of it they speak both languages fine.

I agree with u 100%. I think (in my humble opinion) that its SO much easier to raise a child speaking a language than introduce it to them at an older age. Especially bc kids at the age of 1 or 2 really do mimic everything they do or hear. If you're correctly pronouncing words, the child will be able to mimic what you say, pretty much copying your accent. Plus, when they're that small, the language has a greater chance of being accepted. If you start teaching a child in 7th or 8th grade, they may feel self conscious because of how the words sound coming out of their mouth. OR they may have no interest because their friends dont speak that language.

i'm a linguistics major and that seems to be the most prevalent way in the research papers i've read =)

It's good to immerse your children in the different sounds of various languages when their brains are learning to pick up on the subtle variations.  (The reason Japanese people can't differentiate between L and R sounds is because their language doesn't use them like English does, so they literally can't hear the difference.)

It's been proven in recent years, however, that our brains aren't as hardwired after childhood as we once thought.  So it is possible to teach old dogs new tricks, so to speak.  It's just a little more difficult because you have to make a lot of new neural connections and unlearn certain things.

Learning a language in late adolescence and adulthood can often be challenging if you're not frequently surrounded by people speaking that language and being forced to adapt in order to communicate.  It's taught by rote memorization, usually, in classes that don't even always encourage you to constantly try to speak the new language when you're there.  I think the reason I picked up on French so well back in high school and retained a lot of it to this day is because my teacher only spoke French to us from day one.

My mother raised me from a young age to appreciate my Cuban heritage, so I've been raised speaking Spanish. 

The only issue there was that my mother herself speaks pretty shitty Spanish.. so a large portion of it I've had to learn from tutors.

If I ever had kids, I'd want them to know 3 languages- English, Spanish, and Mandarin (the most common language in the world). 

In the Vietnamese community here of which I am a tangential part, many of the folks who came as refugees and thus had no cultural preparation, have continued to speak tiếng Việt in the home. Their children spoke exclusively the language of the old country until they began to mix with the local kids and started school. They learned English very quickly whether or not they experienced ESL teachers and have grown up speaking both languages well, the Việt with the accent of their parents and English with the accent of their playmates and schoolmates (tempered by the desire to excel and deliberate study). Some parents determined that as new or prospective Americans they must speak only English in the home. Their children grew up speaking no Viẹt and English with a thick Vietnamese accent. Some of the first group have become trilingual as they take Spanish or French in high school and college (which should have been taught from second grade at the latest).

Language affects you the way how you think and definitely is influenced by overall cultural aspects. It is a presentation tool of showing who you are and your upbringing. It is not just about a, b, c word you speak, but rather an object. As a multilingual person, I sometimes feel like people expect differently from me depending on which group of language people I talk to. (f.g. normally i feel more outgoing when I speak in English than other language I speak.)  It could be ok to say something  in one language but hardly ever accepted in another. 

The parents need not be the models of the language. If neither parent is a native speaker, there are enough books, recordings (MP3 files, videos and other content for the kids to learn from. Exposure to the language does not have to mean speaking.

I am very fluent in many languages and feel that the exposure to the language is important. Worrying about correct grammar is not, in my view, important nor helpful.