Small things that may increase your roller coaster's excitement rating are making a part or two go underground. Also, build lots of scenery around it, inside it,, make it really look good. If you're up on the highest peak of a roller coaster, seeing all the trees below makes for a good sight, and so does passing through a tunnel or so.
To reduce intensity, don't make sharp turns straight after a drop, give a few straight segments then have the track bend sideways while turning. Don't include too many corkscrews or those straight twisting tracks. Imagine you're on that roller coaster and picture when you'd need breathing space before the next drop.
Hmm. What does this X button in the top right corner do? Nooooo!!!