Sorry, I forgot to mention the 'how we chose them' question.
Our officiant provided us with a book that she had put together with different readings for the different segments of the ceremony. There were around 20 choices for each segment, and she was also happy to let us choose our own readings if we wanted to.
My fiance and I spent a day sitting in different rooms reading through the book, and choosing our top choices for each. We came back together to go over our choices, and for every one we had at least one in common. We went back to our officiant with the choices, and she helped us tweak things for ease of flow during the ceremony.
It was actually a really fun day, where we got to take time out and really discuss what the readings meant to us, and what we wanted the ceremony to be like. It turned out to be very stress free and fun.
Perhaps you can find a list of potential readings and orders of ceremony online, and go through a similar exercise with your fiance.