Language (through speech) is by far one of the most effective and quickest way for humans to communicate to each other. It is faster than communicating through writing or body language. Yet we take language for granted, because we have grown up speaking at least one language from as young as age one and recognizing language by the fifth month of pregnancy. Language consists of about four levels (phonemes, morphemes, syntax, extralinguistic information) for it to be communicated effectively.
Being bilingual has both its pro and con. The con is that bilingual children have shown to have languages delayment in the syntax (grammatical order) area when compared with monolingual children. The pro is that bilingual children can communicate in two languages and are also aware of language structures and usages.
I grew up as a bilingual child, learning English in school and Hmong at home. Growing up I always struggled with grammatical errors in the English language. Eventually though I finally got the hang of it. Then at the age of twelve I started learning Thai by myself, by watching Thai dramas and music that had English subtitles. It took a few years before I could finally watch the dramas without and subtitles, but what really made learning Thai effective was its similarity with the Hmong language. The first step I took to learning Thai was just getting use to the sound of the language. Then paying close attention to the subtitles and looking for any one word or phrase I heard such as, "No, Where, What is your name?" etc. I would Imitate these words and phrases, until I could recite it from memory. Then I would look up each individual English word (from subtitle) in the Thai-English dictionary. If the English word yield a Thai word, and that Thai word sounded similar to what I heard, then I just learned a new vocab in Thai (I would also be on the look out of encountering these new words again in other Thai movies). Next I would listen to the phrase multiple times again (till it's no longer strange), now knowing all if not most of the words and trying figuring out exactly were that one word was placed in the sentence, at beginning, end, middle, etc and refer back to its English subtitle. This made learning the sentence patterns easier which made learning Thai easier and more effective more me. For example, in English we say, "What is your name?", in Hmong we say (word for word), "Your name is called how?", and in Thai, "You name what?" Both Hmong and Thai have the question particle "how" and "what" at the end whereas English has it at the beginning.