Doha is not a walking city, wait let's repeat that Doha is not a walking city, you got that? In fact with the exception of the waterfront area known as the Corniche you will not see very many pedestrians. The city is expanding are so are the road works projects, so we do not recommend walking or riding a bike as a means of transportation unless you are looking for an obstacle course.
So, what are your options:
There is a reasonably priced public bus service operating on 35 routes. However it is primarily used by construction workers and the schedules can be a bit erratic but should you want an adventure the main bus station located adjacent to the Gold Souq. Go for it!
With bus and walking pushed aside let's look at the main form of transport, gas is cheap in Qatar, so most people get round by car or SUV. From the airport or hotel you can rent a car but we recommended that you make the reservation from your home country or online to be sure you get the best rates. Also please note that you should have obtain a valid International Driving Permit if you plan to rent a car.
If driving is not for you there is the taxi alternative, but again there's a little catch, when you arrive at the airport you will notice a sea of light green colored taxis. We refer to these metered cabs as "Karwas" and although they might seem plentiful at the airport they can be quite difficult to hail off the street or call to arrange pick up. So the quickest and most convenient solution will be "limousine" taxis. These are unmarked and unmetered sedans that you can book from any hotel or can call to arrange pick up from any location in Doha.