Disabled people prefer their disabilities to be irrelevant as they move about in social situations. Judge the person as if the disability were not present. The best advice is to relax and be yourself.
Steps:
Tips: It's normal to be curious as to why someone uses a wheelchair, but let the subject come up naturally. Colloquialisms like, “I've got to be running along,” come naturally to everyone. You'll notice disabled people also use them as part of their routine conversations.
Things NOT to say: “What's wrong with you?” is a question no one wants to hear. The wheelchair is not the person. A person has a disability rather than being a disabled person - “normal” is not the opposite of “disabled.” People “use” wheelchairs rather than being “wheelchair-bound” or “confined to a wheelchair.” If you're curious about the wheelchair itself, ask directly, but remember not to handle it like a car on display at a dealership.