TinyCAD is a great FREE tools to design electronic circuits. It can be found & downloaded at http://tinycad.sourceforge.net/
An important aspect I have learnt is that it is necessary for all components to have the PACKAGE attribute. This means that when you export the components in a 'Netlist'' for use in a layout program the physical characteristics of the components are known. I use VeeCAD as it is good for layouts on stripboard, and that comes with libraries for TinyCAD that make this easier. Just read the VeeCAD instructions.
The package specified on each component must be a shape that VeeCAD knows about