A passport with at least 6 months validity remaining is necessary for entry to Laos.
A tourist visa for Laos with 30 days validity can be issued via a travel agent or by applying to a Lao embassy or consulate. The visa will cost between $30 and $42, depending on your nationality and in which city you apply.
Getting a visa on arrival is easily done at most overland crossings between Thailand and Laos, including the entry points at Huay Xai, Vientiane, Savannakhet, Tha Khek, and Vieng Tao. It is also available at Vientiane, Luang Prabang, and Pakse airports, costing $37, in cash only. You will need one passport-size photo. Visas are also available at the Boten crossing with China and at the main international crossings from Vietnam. Visa on arrival is not available at the Paksan crossing at present, nor the southern road or river crossings from Cambodia. That may change shortly but at the time of writing, if you are planning a trip overland from Cambodia to Laos make sure you get a visa in Phnom Penh before making your way up the Mekong.
You can extend a tourist visa either through the immigration office in Vientiane or through a travel agent. The cost is $2 a day if you do it yourself (Vientiane only). It's a fairly relaxed process. It will be closer to $3 per day if you use a travel agent, which is a necessity if you are outside Vientiane. All tourist visas are single entry only. If you want to stay in Laos longer than a month, it's no problem to cross to Thailand and come back into Laos on a new tourist visa for another 30 days. If you do overstay your visa, you will be fined a fairly hefty $10 a day, which mounts up pretty quickly. If you're calculating an overstay of anything over than a day or two, then you are better off leaving within the expiration date of your visa and crossing over to Thailand to enter on a fresh one.
There is no departure tax if leaving by land on either a bridge or a boat, though one is occasionally asked for an illicit but small "fee" of some sort, particularly after dark or on a weekend. If you're flying out of either Vientiane or Luang Prabang international airport, there is a departure tax of $10, but since early 2009 this fee was being incorporated into the price of the air ticket at the point of sale.
Being very much still a Communist country, what you can and can't take into Laos remains of some importance. Any traveler arriving at either an international airport or any other international land crossing can bring in free of import duties and taxes 1 liter of spirits and 2 liters of wine; 200 cigarettes or 50 cigars or 250 grams of tobacco; and 50 grams of perfume.
A wide variety of goods are subject to prohibitions and restrictions. These goods are defined as products that affect national stability and security, public health, wildlife, endangered species, environment, archaeology, and the artistic, cultural, and historical heritage of Laos. Import and export of articles of national heritage, which include antiques and artifacts such as Buddha statues and images, bronze drums, spears, swords, and bracelets shall be made after the approval of the Ministry of Information and Culture.
The only required inoculation is for yellow fever, if you have come from a country where it's prevalent. While not required, it is wise to get vaccinations for hepatitis A, hepatitis B, typhoid, Japanese encephalitis, cholera, rabies, and tetanus. It's also advisable to update your childhood vaccination series for polio, measles, mumps, rubella, and so on, if you are likely to be around children.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.