It's hard to know where to start. But here are a few basic tips off the top of my head...
Turn off your Flash. The average person leaves their digital camera on Automatic, and ends up Flashing the majority of their subjects. The light from a Flash is obviously artificial and overrides the actual lighting that you see on your subject. Plus, if you're taking a photo of ANYTHING in the distance, your little camera Flash is never going to light it up. I've seen SO many people at Disneyland taking a photo of the castle with their Flash on. Duh.
If you have a "Rule Of Thirds" grid on your camera, use it. It will help you arrange the elements in your shot in an aesthetically pleasing way. Take care to make sure all the horizontal and vertical lines in your shot run parallel with the lines, that way, when you get home, you won't have to waste time Straightening your photos.
http://en.wikipedia.org/wiki/Rule_of_thirdsMake your subject BIG. If you're taking a photo of, say, a person, don't make them this tiny little dot placed randomly in your shot. Either walk towards them or use your Zoom to make them larger. You really want your subject to fill the frame, so it's 100% obvious what you took the photo of.
You asked about taking clear photos on Dark Rides. When Disney do this themselves, professionally, they get to do it the easy way. And the easy way is, you put your camera on a tripod and you put the camera in a static position, NOT on a moving ride vehicle. Disney's photographers can obviously close the ride down, get out of the vehicle, and put their tripod WHEREVER they want. Then all you have to do is turn off the Flash, and do a long exposure of the subject. Your camera will make it look great, automatically.
But, for the average guest who doesn't have this luxury, and IS on a moving vehicle, the best way to do it is to get a high quality DSLR camera, with a large image sensor, and then set the camera sensitivity (ISO) to something like ISO 400 or even ISO 800. That way, you should be able to snap a photo in the dark, on a moving vehicle, without using a Flash, and get a decent exposure with minimal noise.
Anyway, that's all for now. Hope that helped.