You can use graph paper to make an above view of a track layout in the area you have. After you have a layout in mind, section the track off with a highlighter or something. You can use topography on the layout if you are going to have a lot of elevation changes. Make sure you leave room in-between lanes for run-off dirt. You can also use graph paper to make a side view of a sectioned off jump section. It doesn't get much better than this, and it's all accurate. You can pretty much tell how a track is going to be from this. If you are a visual person, you could draw some quick 3D sections for a track. Measure it all, so that it is scale. MS Paint and doodling on paper aren't as accurate, but they take less effort. I scribble things down if an idea pops into my mind. I am very familiar with the size of my track, so I don't use graph paper much at all anymore; I just piece it together in my head and grab a shovel.