Uber or Lyft
Please note, when booking your ride make sure the pickup location (East or West Terminal) is the terminal you are actually in. This is a very common mistake, some drivers will circle around, many will cancel.
The Train
The train is fantastic, costs $10 per passenger. There are many stops along the way that are convenient to a variety of hotels. If you are staying downtown, it takes about 30 minutes to get to Union Station, which is where you can disembark and call a car from there to take you to your final destination.
Renting a Car
The car rental at DIA is a 10 minute shuttle bus from the airport, most of the major rental agencies operate out of DIA.