Hi All! Our oldest son, Gabe, is four years old and has Down syndrome. Kristie and I are continually impressed with Gabe's developing communication skills and we often get compliments on how vocal he is. I thought it would be a good idea to share some of our insights on why we think Gabe is such an excellent verbal communicator. The truest answer is his wonderful mother, Kristie, who has spent countless hours working with Gabe on communication skills. Here are some of the things we have been doing.
1. Teach sign language to your child. No excuses on this one and it's number one for a reason. You might be thinking, "I don't know sign language" or "it might delay speech development." Buy a book and read the book. We didn't know anything either. To get started, the Signing Time DVDs are really helpful, though we quickly found ourselves looking up additional words often. The results of a study by Goodwyn, Acredolo, and Brown (2000) suggest that sign training facilitates rather than hinders the development of vocal language. This was completely true in our experience, Gabe learned the foundation of communication with sign language because we could teach it to him earlier and it cut down a lot on frustrations since we could communicate. We didn't know anything about sign language and we still managed to do it. Baby sign language will be easy and fun for the both of you. By the way, Gabe was understanding sign language long before he could express the signs himself. I think it was over 8 months before we saw Gabe finally sign "more" for the first time and it was a celebration! 
2. Vocalize what you're doing constantly. "Dad is getting the milk out of the refrigerator and placing it on the table. Now I'm taking the cap off to open the milk. Now I'm pouring the milk into the glass." It might sound silly to be vocalizing every action, especially when your child is only a few months old and you're all alone in the house, but it's extremely helpful! Kristie was constantly describing out loud everything she did with Gabe . The vocalization of every action benefited Gabe in developing and understanding the world around him. We still do this all the time in our house.
3. Reinforce the words they are using and continue to develop the conversation with them. For example, Gabe loves trucks and in the beginning would only use one word at a time. He would usually say “trucks” and we made it a point to reply with "blue truck" or "blue dump truck." This tip has a huge variety of applications, the most important developing the conversation by slowly adding more words. We are continually developing the conversation about what the truck is doing.
4. Plan a time and repeatedly have dedicated conversations with them focusing on good communication skills as a whole. This is different than just talking to them. This should be a time to demonstrate a typical one on one conversation. Starting with eye contact and body posture as well as common social practices. Everyday we work with Gabe and practice saying, "Bye Daddy." We are trying to reinforce when he makes eye contact with Dad as Gabe says, "Bye Daddy." Subtle, positive, and immediate feedback is important during this step. When I get home from work, Gabe now asks "How was work, Daddy?" It's pretty awesome to see the connections he's made and seeing our work put into practice. We as parents need to practice using good communication skills; continue to strive to be an example for your child. Don’t expect them to be vocal if all you’re doing is looking at your phone all day.5. Incorporate many types of communication skills into your daily actives. Keep in mind to have a specific reason for why you are choosing to include these elements. Flash cards and books are an excellent place to start and I caution you to not rely on videos, TV, or other digital medium to teach your children good vocal communication skills (though of course they can be used in addition, such as the Signing Time DVDs mentioned earlier). I also suggest labeling things around your house with sticky notes, this helps with reading and sight words and also increases verbal communication because as you see each "sticky note" you can read the note to them and they will in turn know more words and use them in vocal communication.
Therapy has been helpful to us and I am sure many of you are using some type of speech therapy. We want to emphasize the importance of reinforcing the activities from speech therapy at home because those 30 minutes sessions only do so much - it's up to us to implement what they're working on there, at home. We make it a point to do the same worksheets or exercises Gabe does at therapy at home to help reinforce his learning.
I am Gabe's Dad and I wrote this to try to help you increase the verbal communication with your child with Down syndrome. Please know that I am not a medical doctor or speech therapist. These fives tips are based on raising our son Gabe and what has been working for us! Please share, like, or comment if this type of information provides value to you and you would like to see more of it. Thanks and have a wonderful day! Also you can find out more about Gabe and our mission on our homepage found here!
-Alex (Gabe's Dad!)