By Public Transit
The RTD Regional Transportation District (http://www.rtd-denver.com/) operates public transit throughout the Denver area, including buses and light rail.
In 2004, voters approved FasTracks, a plan to significantly expand Denver's public transportation system. However, due to budget problems, this plan won't be fully completed until around 2019 if at all, so public transportation is still somewhat sparse outside the downtown area.
Denver's existing light rail (http://www.rtd-denver.com...) system, though limited, can efficiently get you from downtown to some south central and southeast suburbs. One light rail line travels parallel to I-25 from the southern part of the Denver metro area past the Tech Center, with a small spur on I-225. Another light rail line connects downtown Denver to Englewood and Littleton. Nearly all light rail lines get you to downtown Denver either through central downtown via the Convention Center or to Union Station past INVESCO Field and the Pepsi Center. Light rail tickets must be purchased cash only from vending machines at the stations before boarding the trains. They cost between $2.25 and $5 one way, depending on how far you travel.
The backbone of Denver's transportation system is the buses. RTD buses are $2.25 for a one-way local trip, and with payment you receive a transfer that's valid for one hour after the bus arrives at its end terminal. There is also a free shuttle (http://www.rtd-denver.com...) along the 16th Street pedestrian mall, which is a little over a mile long and takes you close to most major places downtown. More information about RTD can be found at the Market Street and Civic Center bus stations at either end of 16th Street in downtown, or on the RTD website. Local routes denoted by a number crisscross the city, supplemented by 'Limited' buses that stop less frequently on major arteries like Colfax and Colorado Boulevard. These buses are denoted by an 'L' after the route number, and cost the same as a Local route.
RTD also operates limited intercity coach service, mostly to the north suburbs and Boulder/Longmont. These coaches leave from Market Street Station or Civic Center Station at either end of the 16th Street Mall, and will have letters designating their routes. Fares start at $4.00 one way. If you're in Colorado to ski or board on a budget, Eldora Mountain Resort in Nederland can be reached from Denver via the B and N buses.
Airport coaches operated by RTD SkyRide start from Aisle 5 near the terminal. Fares are between $9 and $13 one way depending on your destination. Ask your driver for a transfer ticket as it will be valid on city buses for one hour after your original bus arrives at its end terminal. Buying a round-trip ticket saves you $2.
Make sure to have change before you use SkyRide or buses. Fare boxes on the buses and coaches do not give change, and vending machines at the stations give change in $1 coins, quite hard to spend later. Neither fare boxes on buses nor most ticket machines at stations accept cards - cash only!
By bike
Denver has a large network of bike trails leading all over the city. The city has a fiercely loyal cycling culture, and it's reflected in the abundance of bike lanes and trails in and around downtown. Main trails run along both Cherry Creek and the Platte, and bike lanes run down many downtown streets. The lanes are sometimes dedicated and sometimes run with traffic, and are marked by a stencil of a bike in the street. The city's designated routes are signed, and you can pick up a bike map at the info centers downtown and at many bike shops.
Denver recently launched a bike share program (http://denver.bcycle.com); you can purchase a membership online or at any of the 50 stations throughout the city, choose a bike, and start exploring. Rides of less than 30 minutes incur no fee, while there is a small fee for longer rides.
Don't be afraid to assert yourself in traffic when there is no bike lane - the drivers are, while impatient sometimes, for the most part respectful. Bikes are treated legally like traffic in Denver, and while admittedly rare, you can get tickets for running red lights and stop signs. Bikes are also expected to ride as far to the right as practicable, unless you're riding in a group of 3 or more - in which case you are considered and can behave like a car. Neat, huh?
Bikes are required to have front lights at night, and a good lock is recommended in areas around downtown. Bike theft happens frequently.
By car
Renting
If you plan to go outside of downtown and the surrounding neighborhoods car rentals are the most convenient form of transportation. Local companies tend to offer better prices, but national chains might be more convenient as far as return policies and hours.
Rental companies include most major car rental chains.
Parking
Meters are free on Sunday and run until 10 p.m. on weekdays. After 10 p.m. at many of the meters where it was formerly free, it now is $1.00 per hour from 10 p.m. until 8 a.m. at the new "smart meters." The meters say "overnight parking allowed" but you are still required to pay during this time, or you will get a $25 parking ticket. In the downtown area near Coors Field, The Pepsi Center, and LoDo, there is pretty much no free parking on weekdays. In some areas a few blocks from the city center there are a few non-metered spots within reasonable walking distance of downtown. However, just because you don't see a meter doesn't mean that parking is free. Denver is increasingly using "European-style" meters, where you purchase a paper ticket from a machine somewhere on the block and place it on your dashboard. Also, many neighborhoods around downtown allow only permitted residents to park, so be sure to check the signs first.
It is worth noting that the city government has been cracking down on parking violations recently, so if you park at a meter with a flashing red light and don't pay, even for a few minutes, EXPECT TO GET A TICKET. Meter violations will cost you a cool $25 $50 if you don't pay up within two weeks. Lack of change is no longer a problem, as all the meters in the downtown area are now equipped with credit card readers that accept Visa and MasterCard. $1 will get you around an hour, depending on the location of the meter.
Areas outside of the downtown core 20th St, Speer, Wynkoop St, Colfax and Broadway usually have meters that end at 6 p.m. and are free on weekends, so parking is much easier during those times. The area just northwest of downtown, across the train tracks from Union Station, has free 2-hour parking spots on Wewatta Street just before the Park Avenue bridge.