Step 1: Offer a "documentary" of daily activities while doing them
Providing commentary is an easy way to show your child the meaning of words. For example, when emptying the dishwasher, while the child is watching from a highchair or standing next to you, tell him what each item is. Say things like, "this is a white plate, or this is a fork and this is a spoon." Tell them what you are doing also; that you are washing the glass that was still dirty, or picking up the fork that fell on the floor. All children understand a lot more than we give them credit for, and much sooner than when they can speak for themselves!
Step 2: Read, and keep reading
Reading children's books to your twins is a great way to promote togetherness between them. Not only do the pictures make them want to look, but they will hear the correct way to use punctuation and learn exponential vocabulary skills that will be priceless when school starts. (It won't hurt that they will tune up on the proper way to make animal noises as well.) Are you a literature buff? Share those poems or stories with the children too! They may not understand every word of classic poems or early literature, but they will learn your rhythm and inflection skills, which will be needed later on.
Step 3: Show them the universe!
I called this the universe step because my favorite thing to do when we get out of the car after dark is have the twins find the moon and stars in the sky. I just happen to like the night sky, but this is just the beginning. Ask the babies what color food they are eating, or what they are eating; incorporate relevant adjectives whenever possible. If it's food, try sweet and sour; if you are outside showing them a truck, is it loud or quiet? Show them a ball to kick around-is it red? Is it round? You get the idea.
It may seem silly to some-but talking to your babies and toddlers as much as possible about the events surrounding them will only put them ahead in the race to understand life. We have all heard the expression, "a child's mind is like a sponge," but so many of us get this wonderful sponge, and then let it sit for a year or two before we start letting it work!