I guess it does depend on age. I never took my kids until the youngest was 6 years old. I never talked up an attraction mainly because I didn't know anything about them until we rode or saw it. I never felt that there was anything to be scared of and maybe that transferred to them in some way. I don't really know. What I do know is constant sheltering, even though protecting is part of a parents job, is not doing them any favors. As a parent I always felt that the largest part of my responsibility was to teach them how to cope with the "real" world. Overcoming illogical fears was one of those jobs. I would never have thrown a kid in a parachute out of an airplane, but, a Disney park is hardly a highly dangerous place to be. That was my attitude going in and I think that it helped to not pre-panic a kid before hand.
One thing I did discover, many years later, is my youngest told me that when we rode the Haunted Mansion she had her eyes closed the whole time. She never uttered a peep or a whine or anything, just figured her own way to cope with the situation. The next time she went, the first thing she wanted to see was HM. That to me is a solid step in overcoming fear of things that shouldn't be fear filled.