Shay Williams, Freeskier photo editor
Since delays and cancellations are mostly out of your hands (weather, maintenance, etc.) there isn't too much you can do. However, in the winter, when the weather is more likely to be bad at DIA, try flying out earlier. This is because the planes have been sitting overnight and don't have to get to DIA from somewhere else. You can also use sites like seatexpert.com and seatguru.com to find out what route your plane is on. Picking a plane that flies from DC is more likely to be on time than from a place like LaGuardia or O'Hare.
When it comes to weather, flying in the morning is best. However, if you know the weather will be good, then evenings are best, especially if you are flying west to east. The airport is usually less crowded than midday and you'll get a full day to spend on the slopes in whatever town you're in. And, it gives you more time to get to the airport. Remember, delays can happen before you even get to the airport, especially if you're coming from Summit County.
Printing your boarding pass in advance can help, but since you are skiing, you are most likely checking bags, not carrying on. Sure you can pay your bag fees online and such, and some airlines at DIA (like United or Continental) have special bag drop areas. But if you're flying something like JetBlue or Delta out of DIA, you still are going to have to wait in line to drop your bags, in which case having the gate agent print your boarding document isn't a big deal. All in all, if you're checking bags, printing at home or used mobile boarding docs (which DIA can accommodate but other airports cannot), doesn't save a ton of time.
DIA uses pretty wide scales, that pretty accurately measure the bags. Since ski bags are long, you can try propping one end under your foot secretly as to take some of the pressure off the scale. Also, since the middle of the bag is what physically sits on the scale, try putting a lot of the weight (i.e. your boots) at the very end of the bag so it's not getting weighed directly. That might shave a few pounds.
DIA doesn't make you drag oversized bags to a special drop off bag area, they take it right at that counter where you're checking in. This is good because you don't have to drag your things anywhere. But it's bad because the age old "take 10 pounds out of your bag and stuff it back in on your way to the bag drop" trick won't work.
While the status check-ins (i.e. red carpets, premium lines, etc) are a no-no to general fliers and you'll get kicked out and embarrassed if you get caught. But you can always chance it and hope you get a lazy gate agent. Some might just assume you're a status member without actually looking. That usually means free bag charges and maybe even priority tags so that your luggage is less likely to get lost in transit.
Outside of renting a car or having someone to snag you at DIA, it's not that easy to get to the mountains. Colorado Mountain Express is your best bet. CME picks you up at DIA and will deposit you door-to-door or at a depot in Summit County, Vail County, Eagle County or the Roaring Fork Valley. The cost isn't too bad either. Translation: Shared van/shuttle to wherever you're going in Aspen/Snowmass, Vail, Beaver Creek or Summit County.
As for air connections, DIA services airports like Aspen, Montrose (Telluride or Crested Butte) and Eagle (Vail/Beaver Creek).
If you're in gates 80-90, those are the commuter terminals and expect a walk to or from the main terminal.
If you're flying out of Concourse A, you can walk there, accessing a lesser known security checkpoint that is usually faster than the two main security zones at DIA.
Don't park a car in the Mt. Elbert lot. It's literally in Kansas. Pike's Peak is better and the Garage is the best. But never Mt. Elbert.
Need last minute dress clothes or shoes? The only formal wear place in the whole airport is Johnston and Murphy in Concourse B.
Flying home from an international destination? Even if DIA isn't your final stop, make it your first from overseas. Customs in Denver is a breeze, the fastest I've ever used in the States.
Every 2nd pillar at DIA has an outlet. So if you're looking to charge your phone or laptop, don't crowd your gate, go find an empty one (there are always empty gates at DIA) and you'll be set. Alternatively, the upstairs areas in the main part of each concourse has lots of plugs floating around.
The first and last car in the inter-terminal trains are usually the most full, but they are the closest to the escalators for baggage and each concourse. If you're in a hurry, save yourself some time and hop on an end car, not a middle one.