When I see someone in a wheelchair, should I offer to push the chair?
Think of someone's wheelchair or other mobility device as an extension of their body — you wouldn't just go pick someone up by their legs and walk for them. Mobility devices are used to offer independence, so unless the person asks, it's generally considered rude and invasive to push the wheelchair of someone you don't know.
Is it rude to ask what happened to them?
All people deserve to have their medical privacy respected, including disabled people. If a disabled person wants you to know more about their disability, they will tell you when they are comfortable. In addition to the right to medical privacy, the question in general can be traumatizing or insensitive. Many disabled people have simply been born with a disability like myself, or if their disability was acquired throughout their life, then they may have experienced a traumatizing event. Anyway you spin it, this question is inappropriate.
Should I bend down to talk to the person? It feels awkward, but so does standing up.
There is no need to bend down. As long as they can hear you and you can maintain eye contact, then bending down is unnecessary and can come across as patronizing — even if you have good intentions! The reason we feel awkward is because society is uncomfortable with disability, but disability is not a bad thing! And if you're intentional and examine where that lack of ease comes from, you will be able to pinpoint areas where you can grow and learn to become comfortable with disability.
When it comes to easing life for wheelchair users, what are some positive things to do — holding doors? Shoveling snow?
When you're going to spend time with someone who uses a wheelchair, make sure the place you're going is in fact accessible. Pay attention when you're at your favorite stores, buildings or parks — are they accessible by wheelchair or mobility aid? If not, request that they become accessible. You can send organizations that specialize in making infrastructure ADA compliant their way. Most accessibility accommodations cost $500 or less and can be reimbursed.