Post 4 of the disABILITIES FAQs thread has formation about traveling by bus at WDW.
You can find that thread near the top of this board or follow the link in my signature.
The biggest hint is to practice ahead of time so that you can confidently go backwards, forwards, and turn left and right in both directions. Getting onto the bus is like parallel parking on the wrong side of the street.
My second hint is to turn the speed down - you don't want to be in 'Rabbit' speed getting on.
My third hint is to listen to the bus driver if they give advice. People often turn too quickly.