My wife and I plan to take the Zephr from Denver to Glenwood and back for a 50yr nostalgia repeat trip. Our main objective is to view and photograph the scenery. I understand seating on the upper deck is on a first-come basis and this segment of this route is very popular. How do we go about snagging two window seats when we get aboard? Is it get in line somewhere early, or pick specific cars to run for, or what tactics?