How we discuss disabilities around other people, especially those with disabilities, makes a difference in how they feel about themselves and how others feel about them. Society has come a long way in recognizing socially acceptable terms in referring to those with disabilities. There was a time in our past when "handicapped", "crippled" and the "R" word were acceptable! But we have evolved since then and that language now can be offensive to most.
It is very important to recognize that a person with any kind of a challenge is a person first and foremost. They have feelings, they have goals and purpose in life just like anyone else. Others often inquire immediately about what disability they have or what is "wrong" with them. This can feel very dehumanizing. Those with disabilities may be highly capable and intelligent in many areas of life despite their challenges, but often find that others allow the disability to overshadow their strengths.
We want to be sensitive to the language we use with others but it can be difficult to stay on top of acceptable etiquette when it is constantly changing. This PDF includes a chart of outdated versus respectful language prompts for a variety of disabilities that you may find helpful: http://www.aucd.org/docs/add/sa_summits/Language%20Doc.pdf
One simple thought to keep in mind: Always treat others like you would want to be treated!