After check-in, stay on the upper level and look for the pedestrian bridge (opposite end from the Westin Hotel), located between the Main Terminal and Concourse A. Walk across the short bridge-way, which not only offers one last view of the Rockies, but is also "the only passenger bridge in the United States where people can watch a plane taxi beneath them." You'll then find sparsely populated security lines for TSA PreCheck, premium passengers and general travelers.
Some have said you can pass through security in as little as ten minutes, which is a fraction of the time you can expect to spend in the "regular" security lanes. Once on the other side, you'll exit closest to the Concourse A gates, but the train to take you to gates in the B and C concourses is not far.
