I've been hanging out with infants more than usual lately and am struck by how intent they are when vocalizing. When we respond they listen just as intently. So, what should we be saying to them? Whatever we want to say. We can certainly tell them how wonderful they are, strong, capable and smart. But, we can also tell them about our day or narrate our activities as we go through our day with them. Babies learn to talk by listening to others. They learn the art of conversation from listening to conversations. When I talk to babies who don't yet have words that I understand, I often reply, after they've "said" something to me, "Wow, that's so cool." Or, "I didn't know that." In that way I am modeling a response which is an important part of conversation. Conversation is listening and replying with an appropriate response.
Conversing with babies also signals their importance. We want them to know that we value them, so we pay rapt attention to them. They seek eye contact regularly. That eye contact helps keep them grounded. Conversation also help expand their vocabulary and often encourages them to speak early. That's why it's important not to do "baby-talk" with them. Talk to your baby as though (s)he understands every word. Don't simplify your vocabulary, rather expect them to learn it. People used to remark on what amazing vocabularies my children and grandchildren had at a very young age. That's because I spoke to them as I would an adult. That doesn't mean that I talked about complex ideas, but it means that I didn't dumb down the words I used.
Babies start learning from the moment they are born. They are like little sponges, soaking up everything they see and hear. For that reason, please set aside your discomfort and talk to your baby as much as you can. They will thank you for it, maybe earlier than you expect. Remember that they are real humans inside these tiny bodies, trying to figure out how to communicate effectively. They work very hard at it, too. I think we should match their enthusiasm.