So just my 2 cents worth of what I tried doing with my son (no scientific proof to say these are game changers, but they seem to make sense)
- Talk to them. Talking to them means face to face, with eye contact, and not looking at your phone when mumbling random sentences. I mean talking to them like you would politely with any adult, with full eye contact, expressions and perfect conversational grammar. This is important as research has also shown that a baby who listens to instructions from a person speaking to him will remember the instructions, while another baby who listens to instructions through a radio (audio only) or television (audio and visual but no eye contact) will not.
- Articulate clearly. Which means no more mumbling. I have observed that my son spends a good portion of our conversations looking at my lips. He can hear perfectly well, but he lip reads probably to figure out how he can learn to make the same sounds as I do. So enunciate your words clearly for them to learn, and sometimes exaggerate and open your mouths wider just so they can observe easily.
- Read to them. Don't wait until they can hold or flip the book before you read together. I started reading to my son the day we went home from the hospital. I sang to him as he nursed, but because he nursed for 40minutes each time, and 8 times a day, I ran out of songs that wouldn't bore me. I ran out of new thoughts because I was exposed to nothing else besides him. So I read books. Since he couldn't see yet, I read books that I myself would read. That included Reader's Digest, novels, business books and even encyclopedias! Just keep reading and he will learn something. I had secretly hoped that he would even remember a thing or two from the encyclopedias that I read, but I will leave that for another post on "How to Raise a Genius". LOL
- Think aloud. This allows you to talk to your child a lot more than normal. Your brain is always active and thinking about something, and if you verbalize your thoughts while having eye contact, it's like having a permanent conversation with your child. So you can never say you have nothing else to talk about. Examples could be "what should I have for dinner tonight? I have 2 carrots that I bought last week, and a tomato left. I'm craving some hot soup, but I will need some potatoes to go along..." yada yada yada. Or "I haven't been out shopping much lately, how about some online shopping later when you're asleep? I should check out the latest sales on Amazon... or get that juicer that XXX mentioned on Facebook!"
- Use simple words. They are, after all, still babies learning a brand new language. Use simple words repeatedly so they can grasp the context which it is used it, and learn the meaning of the words.
- Speak with perfect grammar. Babies learn language from a young age - this means not just vocabulary, but also grammar. If you use baby babble or broken English just to emphasize certain words, your baby might end up learning a bunch of nouns but have trouble piecing them together in a grammatically correct sentence. Language learning starts young!
- Vary your vocabulary. It is tricky to keep repeating the same words to help them learn a new word, and at the same time remember to vary your vocabulary so they learn more. But one very common phrase is "Good Boy!" Regardless of what the baby did, parents and grandparents always exclaim "Good Boy!" Sometimes, being more specific helps. For example, "That's an obedient boy, thanks for putting the toys back into the box!" or "Well done, you finished your meal!" That gives more meaning to your praise, is more specific so your child knows what he is being praised for, and also helps broaden his vocabulary.
- Be bilingual. This is a result of some studies performed by the Infant and Child Language Center, NUS, which shows that bilingual children learn faster than monolingual children.