Route decisions: Can I find the way to where I want to go?
Mental mapping: Are my experiences consistent and understandable enough
to know where I've been and to predict where I should go next?
Can I make a coherent mental map of the spaces I have seen, and use it to predict where to go next?
Closure: Can I recognize that I have arrived in the right place?
And then, think about design in the larger sense, how good design helps us do what we need to do, and poor design hinders us.
Think about it while planning your site.