I've found that wooden coasters tend to keep their speed really well, so the way I build good ones is to have a steep drop that goes back up to within 1-2 of the total height, and then work my way down only 1-2 at a time from there. Make them twist through their own structure a lot, and going underground is always a help. I've also found that using the 45-degree turn is much less intense, and the coaster seems to keep its speed better, so use all different types. I generally have the great majority of the turns banked to keep the intensity lower.
Hope this helps!
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/index.html
