When we stored boats for an extended layup we ran a heavy dose of fuel stabilizer during the final run of the engine so that the fuel/stabilizer mix got sucked into the carb bowls. We also "fogged" the engine with fogging oil during that last run so that the cylinder walls were coated and would resist being rusted. We also changed the oil and filter, and sprayed the entire outside of the engine with something like WD 40, Corrosion Guard, or CRC 666.

If the engine you are going to store is only being laid up for a year or less you probably wouldn't have to take the pressure off of the springs, but it sure wouldn't hurt.

Don