coil over springs

A while back there was a discussion on choosing the correct spring for a coil over. If memory serves, this is the short version:
1 install the recommended length spring on the shock
2 using the threaded adjuster, compress the spring 1 inch
3 install the shock on the vehicle and set it on the ground
4 if the spring is correct, the shock will now be at manufacturer's recommended installed length.
Is this correct? or am I way off base?
Thanks for your input

You are correct... that gives you 1" of
movement each way