While you can be assured that you need not sit down and attempt in any formal way to teach your child every word he needs to know, there are things you can do to encourage language development -- and it's almost certain that you are doing them already!
Language development requires plenty of opportunity for the budding speaker to interact with other people. While a baby might well be able to learn new words from television, for instance, she wouldn't be able to learn to talk simply by watching television. Hearing your speech in response to hers, your baby can enrich and correct her own language.
However, this doesn't mean you need to become the speech police, correcting every mispronunciation or improperly used verb tense. But you can gently and constructively shape your child's speech as you name objects and interact with him. A conversation between the two of you might go something like this:
Mom: "That's right, that's our dog over there."
Mom: "Mm-hmm. Our dog's name is Maggie. This is Maggie's water bowl."
Baby: "Goggie bowl."
Mom: "Good! That's the dog's bowl, Maggie's bowl."