Instructions
Go to Nolimitscoaster.com and download the free coaster builder. There are other games or simulations you could use, but this one is free, and comes with a great deal of detail for creating a "No Limits" type of coaster.
Open up the simulation and go to the coaster editor. In this program you can select your particular terrain such as mountains, waterfalls and lakes, along with more than 65 different track pieces that you can mix and match in whatever way you wish. Place your terrain and track in the arrangement you want by clicking on the piece you want to add, and then placing it in your field to make it part of the track.
Check your track to be sure that it's complete and that all parts and pieces are connected as you wish them to be. Once your coaster is complete, click the "Start" button to run the simulation and see how your coaster works when a car goes down the track.