UBD and Me

What are the most challenging aspects of the UbD design model for me so far?
I am having trouble clearly defining what my EU and EQ are. I want to understand what assessments work better at what stage of the learning.

What are the challenges in articulating and framing a big idea? (think about our Hanukah discussion!) How to make it clear and concise and yet be broad enough to encapsulate a big idea that can be transferable.

Can I see what the big ideas are in the curriculum in my classroom? Why or why not?
I can see them when I look hard enough or look at the central ideas exposed in the various topics (books) discussed.