Decide where and how to get your tourist visa. Tourist visas are now valid for 30 days (up from 15 days) and cost approximately $30 for Americans. You can arrange these with the Lao Embassy, either in the US or in one of Laos's neighboring foreign capitals (Bangkok, Hanoi, Phnom Penh). Visa service on arrival is available if you enter the country by flying or by crossing overland at Luang Prabang or Vientiane. Remember to bring exactly the amount of money you need and a passport photo for that. There is no visa on arrival available for the overland crossing at the Lao-Cambodian border (Stueng Treng to Si Phon Don).
Make up your mind about whether you want to bother with anti-malarial drugs. Some people have truly awful reactions to anti-malarials, and you don't want that suddenly appearing on your vacation. On the other hand, a good rule to apply any time is better safe than sorry. The best advice is that if you decide to do without, be vigiiant with your mosquito precautions (bug spray, burning insect coils, etc.).
Plan your itinerary carefully. Laos can only be improvised if you have a lot of time to spend there, because there are few roads and many of them are winding highland affairs. Bus travel from point to point is typically either an all-day or all-night trip. Also, where you go may depend heavily on whether you are going on to another country after Laos. Going to Cambodia? You will want to exit in the south. Going to Vietnam? You will want to finish up in Phonsavan and the Plain of Jars. The main thing is to avoid doubling back at any time, because that will eat up an entire day.
Save storage space. The night market in Luang Prabang has excellent handicrafts, especially silks. Make sure you have some space in your bag to carry some purchases away.
Bring a reserve of cash and traveler's checks. There are now ATMs in Luang Prabang and Vientiane, but they are only truly reliable in Vientiane. There are reports of an ATM in Pakse, but this is strictly a transit point and not really a destination in itself. You will need to plan for the possibility of arriving somewhere and only having whatever money is on your person, just like in the old days before the ATM became internationalized.
Stay cool. Losing your temper in a Buddhist country like Laos is bad manners and causes a serious loss of face. No one who sees it will take you seriously from that point forward.
Don't buy drugs. Even though drugs are widely available in Vang Vieng, they are generally illegal and possession is subject to a $500 fine, payable in cash and on the spot. A good rule of thumb is if they are not a part of the food or drink offered at a restaurant, don't buy it, and absolutely do not leave that establishment with it.
Avoid sex with the locals. Sex with Lao women outside of marriage is illegal.
Don't criticize the Lao government or Communist Party within earshot of a policeman or official.
Take your shoes off before entering any building.
