Take a long, hard look at the 50 Pre-Made Parks that Neversoft donated to the cause. They're expertly designed and there are enough flavors so that you'll probably see something approximating the park you want to do. Mix it up. Try to place both vert and street in your course. Not only will this make for bigger point possibilities, it will have more overall appeal for the variety of skaters who will skate your house.
Place risers first.
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.