Uyuni a small town situated in the middle of nowhere. It originally blossomed as a railroad junction, and even if this is still an important aspect, no doubt is tourism now its main source of prosperity. What would otherwise be a fairly dull stopover en route between Salta, Argentina and La Paz or Potosí, has become absolutely mandatory. The sole reason: salt flats, the world's biggest. (See Salar de Uyuni).
Plan to arrive a day or two before you intend to depart on a salt flat tour, especially if there are only 2 of you. That gives the chance to meet other travellers, thus a larger group has more bargaining power for the 'daily rate'.
TAM flights to La Paz (via Sucre) several times a week. Currently (July 2015) you can't buy a ticket online but they have office in the Uyuni centre.
Amaszonas is also servicing Uyuni. There are three flights per day and cost about $250 each way. However, for many the Amaszonas is the worst airline in South America. It's very often late, usually by 2-3 hours. In these occassions Amaszonas doesn't care at all and provide passengers absolutely nothing.
To sum it up, you pay fortune just for a one-way 50-minutes long flight which is at the end slower, less comfortable and ten times more expensive than an overnight bus. I strongly recommend you think very hard before booking any overpriced flight with this unreliable and unprofessional airline. Rather get a flight with TAM instead.
You will need around 12 hours from La Paz, by bus. The bus ride with worse operators can be bitterly cold in winter - travellers have been known to sit in their sleeping bags on the night bus from Oruro to Uyuni. With other companies (Todo Tourismo, Trans Omar and Panamerica Sur) it's much better. There is direct line, heating and toilet. Buses to Oruro/La Paz are often booked up in advance - you likely need to book at least the day before, several days if you wish to take the comfortable tourist bus or one of the better bus companies - best to do this before going on a Southwest Circuit tour (if coming from San Pedro de Atacama, be prepared to spend a night in Uyuni and have little choice of bus company).
There are several buses daily to and from Potosí (4 hours, 30 Bs.), from there you can go one to Sucre (3 hours more). There is also a nightly bus to Sucre leaving at 9 p.m., arriving at 3:30 a.m., for 60 Bs. Beware however, companies such as Transporte 11 de Julio have been known to cancel buses without notice, and without even opening their office to explain. As of June 2014, beware of companies such as Flecha Bus selling "direct" tickets to Sucre, when the bus reaches half-way in Potosi, the bus driver claims the service ends there and will try and make you go all the way by taxi, this is a scam, you should ask for ALL your money back from the bus driver and get a taxi if you´re stuck in Potosi to Sucre(3hrs about 40B each).
Many daily departures around 5:30 - 6:00 AM for Tupiza, stopping halfway for lunch in Atocha, 7-8 hours, 60 Bs. Three days a week there are 9 AM departures, and occasionally a Land Cruiser departs 6-7 PM, -ask around. Although the train is definitely smoother, and somewhat faster, this bus ride offers terrific views.
Trains of Ferroviaria Andina [www.fca.com.bo] run south to Villazon on the Argentinian border, stopping in Tupiza and Atocha. Northbound trains go to Oruro. The formerly existing train connection to Calama, Chile has been discontinued. The views from Oruro to Uyuni are interesting - the train goes over the Poopó lake (with flamingos), then over the altiplano (terrain and towns are quite depressing), you can see nice sunset on the way. Expreso del Sur (better class) trains leave from Oruro on Tuesdays and Fridays at 15:30 and arrive 22:30 to Uyuni. You can select executive and 2nd class (Bs 56) tickets in Expresso del Sur. It's best to buy the tickets, i.e., 5 days in advance to have a seat - for this you may contact the company offices in La Paz. The other Train Wara Wara leave Oruro on Sundays and Wed at 7pm and arrive in Uyuni at 2:30 am.
Museo de Arqueologia y Antropologia, Arce (Half a block from the clock tower). Quite a few skulls and a handfull of mummies, plus some less exciting stuff.Bs 2,50. edit
Despite its modest site and geographical isolation, Uyuni is worth an hour or so walking around. Particularly the Avenida Ferroviaria has many monuments, mostly railroad related.
Allegedly Bolivia's first locomotive, stands in the middle of Avenida Ferroviario, by the corner of Calle Santa Cruz. The first locomotive is in Pulacayo almost 20 kilometers on the road to Potosi. Used in the Huanchaco mine.
Train Graveyard - a couple of km south of town, by the railway to Chile, there are dozens of old, rusted locomotives, a few wagons and some other antiquated machinery. Usually a stop on salt flat trips.
The salt flats, Salar de Uyuni, can be visited on daytrips, or longer trips, up to 4 days, including a swipe down towards the Chilean border and the lagoon and geysers of that area. You can also reach the salt flats by local bus for a hike.
Make sure that you point out that you only wish to go with a responsible driver; there have been reports of drunkenness among drivers that may be averted with continued pressure on the tour companies before departure.
Small eateries, (first floor of the marketplace building). Cheap typical breakfast.edit
For a cheap lunch (10Bs for soup and main) head for any little joint with the sign Almuerzo outside.
Minuteman Pizza - Ferroviaria 60, Uyuni, 591 2 (693 3186)  Hours: Breakfast Buffet 50bs. 7:30-10AM , Dinner 5-10PM Within the Tonito Hotel, backpackers congregate here in the evenings (enter through the hotel reception, this keeps wandering petty thefters from entering). Large variety of pizzas (including spicy llama), great breakfast, English-speaking owner, travel-book library. From 45 Bs for an individual pizza. Just don't arrive too early for dinner - the people running the hotel were incredibly rude and refused to let us wait 30 minutes in the lobby for the place to open.
Pub-Pizzeria-Restaurant ARCOIRIS – Avenida Arce 27, Uyuni, 591 2 (693 3177) ; English / Italian - speaking owner ( Willma ); Hours: 3-12PM; Pizza & Pasta (Italian taste), typical local plates, some time live music.
Pizzeria Donna Isabella, Corner of calle camacho and calle colon. Not cheap but not expensive either. Everything is delicious and house speciality quinoa pizza is worth trying. edit
Tonito Hotel, Ferroviaria 60, Uyuni, 591 2 (693 3186)  Mid range hotel in town. Rooms are situated around an internal atrium area. Clean rooms, solar or electric-heated showers, transportation from train station available, book ahead in the high season. New rooms with solar showers and heating. Only hotel with wifi (very slow, however) and american buffet breakfast. Double with private bathroom, 400 Bs (as of May 2012).
Hostal Sajama, Potosí 35, 693-3099. Cheap place with basic clean rooms. May be cold in the night. Single with shared/private bathroom Bs 25/40. NOTE! On May 30, 2007, two Canadian students visiting Uyuni were found dead in their rooms at this hostal due to carbon-monoxide poisoning from their gas heater. 
Hotel Avenida, Ferroviaria 11, 693-2078 , clean and inexpensive in the town center, near tour operators. Only two hot showers, but the door to one is often locked. Single with bath 60Bs, Double/Matrimonial with bath 100Bs.
Beware of the cheap hostels near the bus offices. If you arrive in the early morning these places will charge you a full night for your stay until 12PM (noon).
Hostelling International Salar de Uyuni, Calle Potosí esq. Sucre, Uyuni. There are reports of poor service, unbelievable levels of rudeness and management not honoring bookings, in fact literally shoving booked guests into the street late at night. Horrible staff who acts like they don't need customers. Strange rules with taking showers (like 1 shower per person per night). Rooms are dark and old. 100bs per room with shared bathroom (19.12.2012).
Hotel Girasoles, Av. Santa Cruz 155, Uyuni, phone: 026933323, price (double bed): 75$ double
Hotel JULIA, Av. Ferroviaria # 314,Uyuni. Clean, but quite expensive considering the room size and quality. The hotel has singles, doubles, twin, triple, quadruple and rooms with share and private bathrooms. In July 2015 the price for a double room was 200 Bs (shared bathroom) and 300 Bs with en-suite. Very poor breakfast, one of the worst in Bolivia. Small radiators in bathroom and room, but only turn one for few hours at night. TV cable (Spanish but some documentaries can be in English with Spanish Subtitles). It also has a living room with TV and tape recorder, a computer room (Fees) and a storage room (free).
Note: Speak Spanish only. Nice staff but a bit disorganised. Room can get a bit cold at night. Sheets smells nice laundry products. Soap, towels and toiler paper provided.
Piedra Blanca Backpackers Hostel,Av. Arce # 27, Uyuni". Double with private shower/WC for 280 Bs including breakfast (July 2015). Speak English and Spanish. At the time of staying the walls had peeling paint and room were basic with no TV or furniture but had a small radiator that can be plugded. Liquid soap, nice fluffy towels and toiler paper are provided.
Hotel Luna Salada, Salar de Uyuni (By the entrance of the salt flats.), ☎ (591) 71212007. High-end hotel at the entrance of the Salar de Uyuni. Walking distance from the salt flats.edit
There is now a Banco Credito ATM in Uyuni, on Calle Potosí. WARNING: this ATM will fail silently if it runs out of cash. Your card will still be charged, you will not get your money and the bank staff will be 'unable' to help you even if you speak Spanish fluently.
Prodem gives cash advances on mastercard or Visa creditcards with a 5% commission.
You can get cash out of an ATM indoors at a bank with Maestro. WARNING: on weekends the ATM runs out of cash stranding tourists who counted on that ATM for money. Bring an extra stash of dollars just in case.
There are several casas de cambios to change travellers' checks or dollars, euros, Chilean pesos or Argentinean pesos. If you are heading to Chile, get rid of your bolivianos, as the exchange rate on the other side is much worse.
One of a handful of laundries, Laundry Huila Khota at Av Ferroviaria 257 (by the homonymous hotel), has same-day service at 15 Bs per kilo. Lava rap is the biggest laundry service for 15 bs a kilo.
The cheapest international phone calls seem to be at Call Shop Uyuni, Av. Arce, 30 metres from the clock tower. Bs 2,50 to most of the world. Internet here is expensive, though, at 6 Bs an hour.
Get the exit/entry stamps you need at the immigration office now on ferroviaria inside the old cine.
There are several slow internet places for around 5 Bs. per hour. Quite fast internet you can find in Hotel Julia.
If traveling by (rental) car, find and pay for a gated and secured car park. (Or you may lose some external parts.)
Salar de Uyuni - with over twelve thousand square kilometers, is the largest salt flat in the world. It can be done as a daytrip, or with a few overnights, often combined with the lagoons and geisers closer to the Chilean border. Instead of returning to Uyuni, you can opt for San Pedro de Atacama or Tupiza.
You may want to visit hot and lively lowlands. To save yourself a day or two of mountain ride (some segments may be tough for your body) look for a flight directly to Santa Cruz (city, Bolivia). Amaszonas (Bs 1500) and TAM (Bs 600) have offices in the town and offer flights, but not every day - check the schedules.
Remember to get an exit stamp in Immigration Office in Uyuni (the date on the stamp is the expected exit day, so you may get Chilean entry stamp with earlier date). The Immigration Office is open 7 days per week.
If you plan to go Chile, you can get transport onwards to San Pedro de Atacama instead of return to Uyuni. The price is usually around an extra $10USD. Some tours include this in the tour price, ask first. Note that this, depending on tour operator, means getting up very early (and convincing everyone else to do so as well) in order to be able to see all sights before heading to the border - failure to do so means a risk of missing the bus connecting to San Pedro de Atacama.
Bus/Train may be taken to Avaroa station near the Chilean border, from there the border may be crossed to the Chilean Ollagüe, where another bus/train may be taken to Calama, etc.
Note there is an exit fee to be paid at the Bolivian border control—have enough cash.
Also note the Chilean customs officials are very strict in their inspection—read carefully the customs form and be careful to declare everything in your possession, lest you be facing charges for attempting to smuggle in your cooking condiments.