This is a trick
that I learned from my parents
... talk to them like people
I know, this sounds kind of self-explanitory, but think about it. When you see a little baby, do you, like much of the world, regress into ittle-bittle baby talk? Do you add -ittle and -oosie and -owsie to the end of all of your words? Do you actually use words like snugglekums?
Now, do you use those words with your colleagues at school or work? Do you use them with your significant other (although that's an entirely different rant)? Do you use them with your parents?
Then cut it out!
Children, while they are small, are not stupid. They hate being condescended to and, once they realize how differently they are treated from adults, they begin to show it. Studies have shown that children that are condescended to, that are treated with baby talk and oversimplification actually develop slower than children who are surrounded by people that treat them like adults with a smaller knowledge base.
My parents always talked to me as if I were an adult. They would talk exactly how they would around their co-workers and friends and, if I didn't understand a word, I was encouraged and expected to ask what it meant.
Because of this, I entered life with the assurance that I was smart enough to understand anything, as well as with a vocabulary and reading comprehension that far outreached my rather mediocre education.
It's hard to start a complete paradigm shift in how people in America treat children by myself, but I'm giving it a shot. And, every time I talk to a six year old and see that gleam of thanks in their eyes when I don't treat them like a lobotomized ape makes it worth it.