To find out what stairs you can currently challenge someone in, first go to the Main Stairs Page, then click on "Show your stairs only" link. The ones in BOLD are ones you can make a challenge in. .
One of the biggest difference I can see with the Stairs rules as compared to the rules I have seen for ladders is how one moves up and down.
1. Nobody can be on the same step/ladder position at the same time.
2. If you win you take the position of that person on the ladder, and everyone shifts down.
Not to say that what I have seen is better is what I am used to.