Simple basic steps to take will help ensure the lift will be ready for operation. If the lifts are going to sit for more than a month I would spray fogging oil into the intake with the air filter removed while the engine is running. Make sure the lift is sitting where you can leave it as you do not want to run after spraying the fogging oil in. This coats the valves and cylinders to reduce rust build up and help with easier start when you are ready to use. Disconnect the battery to remove any draw from the lift. Apply grease to all exposed cylinder chrome to reduce corrosion. If the lifts are sitting on level floor I would leave the parking brake off so nothing locks up. If there is a chance they can move or be hit causing them to move, set the brake. If sitting for a short time fill the tanks and apply a bio guard to reduce build up. Lube all fittings and hinge points so nothing seizes from sitting. Now everything list above will be for a long term storage of three months or more. If you will be using every other month I would just start them once a week and let them run while operating all the hydraulic functions. Keep the tanks full of fuel. This will ensure the batteries stay charged and the lifts are ready to run when needed. If you will be storing them over three months at a time, I would hook everything up once every three to four months and start the lift and complete an operational check, then set it back up fro storage. This ensures everything is ready for operation and helps lubricate all the seals so they do not dry out. I am sure others will add comments on things I have missed. Good Luck.