The tombs of the Valley of the Kings are one of the many essential must-sees in Luxor. They are located on the edge of the river valley a 15-minute drive from the dock on the western bank of the Nile. It doesn't much matter how you get there -- escaping the crowds and the feeling of being shuttled around just isn't going to happen. This is one place where (unless you want the flexibility to roam other West Bank sites) you might just as well take a bus tour. Take water and a hat -- even in the relatively cool winter months, it can get hot. If you arrive at the bus parking lot without something to drink and headgear, head over to the mall to your left (facing the orientation center). Everyone will tell you that you're going the wrong way, but ignore them. You'll find a couple of stalls here that carry what you need. The prices are exorbitant, but it's better to part with a couple of extra pounds than dry out in the hot, dry valley above.
The orientation center at the bus parking lot is worth a 15-minute tour. I particularly enjoy the black-and-white footage of old excavation work, but there is also a good deal of very useful information on the placards on the walls. Before you head out the back to the ticket booth, be sure to check out the transparent topographical map of the valley -- as you wander through the tombs, it's hard to form an idea of what the whole valley looks like unless you've seen this first.
Tickets for the tombs and for the little "train" (really just a converted airport baggage tractor) up to the valley are purchased separately from a booth around the back of the building. The train is definitely worth taking, at least for the inbound, uphill leg. The extra tickets for entering the Tomb of Tutankhamun aren't purchased here, but at the upper office where the train drops you off. Whether these tickets are worth it is subjective -- the tombs are smaller and less colorful than the others, with a lot of fungus on the walls and ceilings. The price of getting in clearly reflects more of a desire to cash in on their fame than their actual interest value.
Keep in mind that your ticket is good only for three of the tombs, so choose wisely. The most spectacular three are those of Horemheb, Seti I, and Ramses III, but because tombs are closed on a rotating basis to protect them from the damaging effects of visitors, one or more of these may be shut when you get there. The least interesting in my opinion are Thawsert, Thuya, and Seti II. The tomb of Amenhotep should be avoided if you're already hot and tired -- it is one of the deepest in the valley -- as should the otherwise fascinating Tomb of Tuthmosis, which is only reached after a steep climb up a metal staircase.