Also, what kind of wheelchair, manual, electric? Do they need it all the time or just some of the time?
Daily situations can be very different as well, are they single, with a partner, carer, kids etc... do they have to use public transport (try getting on some of the city buses in rush hour with a wheelchair!), is there access to special low floor buses etc...
Do they work? Is money a factor, what kind of equipment and aids can they afford? Can they get the lastest lightweight, more comfortable etc... equipment or do they have to rely on what they are given.
All kinds of things.
I also came across some wonderful people. I remember being with a group of the guys and some other volunteers one Christmas Eve and going into a cafe. After sorting the tables and chairs out a man sitting reading a paper caught my eye and asked if I was having a good Christmas, I smiled and said I was and he finished his drink, came over, slipped me a �20 note and said to get everyone whatever drink they wanted on him.
It might be best to pick a condition if you want to be more specific and target your research. Biographies may help and I can highly recommend doing some voluntary work. I can highly recommend Vitalise.