One of the easiest ways to start working in 3D space is by creating a 2D drawing.
Well…let me expand on that a bit. Multiple 2D drawings of the same object from 2-3 or more views. By creating these views and then importing them into your 3D software of choice, you can use them as a road map of all of your curves. In Rhino, the command is “Pictureframe”. This enables you to select an image file, import it into Rhino as a surface and position in appropriately so you can draw over the line drawing. You can use multiple underlays in the same file to bring in multiple iterations of the same subject. For instance, you could bring in a different table leg design, trim back the original legs and place the new underlay in place.
Don’t forget to lock the “pictureframe” underlays as well. It can get kind of maddening to try and select curves when you have a bunch of surfaces in your way. Better yet, group your underlays together, put them on one layer, then lock the layer!