Here are my sophisticated "tools" 
The grid is 1" by 1" blocks, representing 2'x2' actual.
This first one is for when I have 2 levels. it represents the top plateau and the various shaped ramps going up to it. I don't use these any longer since they use 27" curves which my tin-plate trains can't handle.
these shapes help my determine angles coming out of curves.
I use washers in the correct diameters to represent the 27", 31" (O), 42", and more recently but not shown, 54" and 72" curves.
The white cardboard piece is lined off where each segment is one O27 regular track. The string is marked in 1" (2' actual) lengths to help me determine lengths of sidings and such. the blue rectangle represents a 4'x8' piece that I use when determining placement of the plateau. Since I now have bigger plateaus, I use more up-to-date pieces now. I guess I should have included a picture of a ruler too since it's my main tool now.
The grid matches the size of my living room with air vents, outlets, doors, windows, etc noted.
Pretty advanced stuff, huh?
I should really take new pictures to show my current set of 'tools'. Those above are for when I still did 27" curves which I can no longer do with my tin-plate. But I guess the idea gets across
- walt
