Getting to Luang Prabang
By far the easiest way to get to Luang Prabang is by air. Thailand's Bangkok Airways flys almost daily from Bangkok to Luang Prabang. For domestic air travel, Lao Aviation is the only carrier, and flys to Luang Prabang from both Vientiane and Phonsavan. Lao Aviation has a somewhat spotty safety record, but has recently taken steps to improve the situation and upgrade its fleet.
Road travel used to only for the most adventurous, as few highways were paved for their full distance. The road between Vientiane and Luang Prabang is now completely paved, and there is regular bus service between the two cities, as well as Vang Vieng in between. Note however that incidences of banditry are regularly reported on the back roads of Laos. The US State Department has issued repeated travel warnings cautioning citizens about road travel in Laos. While such travel warnings often seem to over state the danger, in this case, you may well want to consider carefully whether or not to travel by road in Laos.
Boats up and down the Mekong are an increasingly popular mode of travel. You can travel downriver from Thailand to Luang Prabang as well as upriver from Vientiane. Although speedboats can make the trip from the Thai border in just a few hours, this is probably a trip best taken slowly. Various operators offer two and three day cruises between Chiang Kong in Thailand and Luang Prabang.