Most visitors will have to stop here over-night on the slow-boat trip to/from Luang Prabang. It`s also possible to arrive by speedboat en route to the north. Much more uncomfortable than the slow boat, however you will arrive before the slowboat so you have the option of choosing a guesthouse and showering with no lines/queues. You also get to see the town as the only Westerner. Another possibility is to reach the place by bus-- this is a rough and long option.
By ship
The boat-landing is at the end of Road 2 on the Mekong. Slow boat leave in the morning in both directions. They depart when full but expect to start at around 9am. Arrive early to get one of the better seats as far away from the loud engine as possible. The dropping off boat normally arrives at about 5pm, but this is Laos, so bear in mind that this is a guideline. Laos transportation goes when the driver can be bothered. It's best just to relax and enjoy the peace and quiet. And have a beer, of course.