But the most important thing to do is to experiment. Try every combination of crazy pieces you can think of.
We have this blueprint testing zone where you can try out your madcap ideas in an open area. It has a much taller height limit for your coasters. Now, I don't mean that the wooden clown telling you "You Must Be This Tall To Ride This Ride!" has raised his outstretched hand a few feet higher. I mean that you can build the most ridiculously tall, skyscraping tower of thrills imaginable.
Remember - the taller it is, the longer the drop. And the longer the drop, the faster that sucker's gonna go...
So try out your crazy ideas, because practice makes perfect. I could tell you how to build my personal favorite coaster...but the best coasters to ride are always the ones you make yourself.