Scrub sap and dirt from the blades and handles with a stiff brush. Use warm water and a squirt or two of mild dish soap for cleaning. Rinse the detergent from the blades with clear water.
Inspect the blades for rust. Use fine-grit steel wool to buff and rub off any rust spots on the blades.
Combine one part bleach with nine parts water in a pail. Submerge the blades in the bleach solution for three minutes. The bleach disinfects the blades, killing any lingering plant disease organisms. Wipe the blades dry with a clean cloth after disinfecting.
Dip a rag in a lubricant and rub a thin coat of oil on all the metal surfaces. Spray the hinge and spring mechanism with a spray lubricant.
Sand any rough areas from wood-handled secateurs using fine-grit sandpaper. Rub boiled linseed oil into wooden handles so they don't become dry, which can cause cracking and splintering.