Great advice Hazel! Planning ahead is even more important for travelers who have a disability. I have written a couple of articles for families of children with special needs who are traveling:Airline Travel and Childhood Disability Weekend Getaways and Vacation Travel with Children who have Special Needs
One suggestion I would make is that caregivers or companions be well informed of the availability of accommodations while traveling and at your destination.
Also, if you have a disability parking placard where you live, carry it with you no matter where you travel in the US or around the world, so you can access designated parking places everywhere you go.
In our state, a person qualifying for a disability parking placard can request two; one for the car and one for your purse, when someone else is driving. When traveling, it's so much better in any kind of weather to park close and have your companion with you rather than dropping you off and finding a spot far away, then hiking out to that spot afterwards while you wait on the sidewalk among the crowds in the dark, or inclement weather. Of course even that is better than missing an event or other wonderful experience!
SE of Seattle