Here's the deal. Don't ask someone with a mobility aid/larger medical devices to exit the elevator so you and your friends can get on together. Technically, they should be getting first dibs while waiting for the elevator as well.
If someone with a device asks for your seat on the bus, let them.
If someone walks into the bathroom with an obvious medical device that requires space, give them the handicapped stall.
According to the ADA, service animals are considered medical devices too.
On the note of service animals, do not take pictures of them, do not try to interact with them, and be understanding that they need space. Ask the owners if you can pet them, but don't get butt hurt if they don't let you.
A lot of this is common sense; you're in college, use your brains.
Thank you for attending my TED Talk.