Since these objects can hold others on top of them, it is important that they go down first. Wherever you throw down your risers will determine the style of course you're creating. Conserve memory by using big pieces. Instead of stacking a bunch of little pieces next to each other, use one big piece that equals the sum of the parts. Be smart about object placement.
Pools are big and wonderful, but they can easily get in the way and disturb level flow.
These are the easiest objects to abuse. The first park I tried was horrendous for this reason. I put a group of penpendicular rails perpendicular. It was a mess. Rails are best when used in conjunction with other lips or looping the backside of an object.