Your maintenance procedure for circuit breakers should begin with inspection. That includes such things as:
Inspect breaker cubicle for signs of arcing or flash. Note any issues.
Visually examine conductors for discoloration and signs of insulation damage.
Look for signs of insect or rodent invasion in the surrounding panel.
Look for any broken parts, loose hardware (e.g., a bolt on the floor), and other signs of mechanical damage.
In addition, follow the manufacturer's guidelines for:
Testing and inspecting mechanical linkages and other components. Don't try to fix these; order replacements.
Cleaning mechanical components. The main issue here is to prevent actually spreading grime via improper cleaning.
Lubricating mechanical components. Use the specified lubricant, not whatever's handy. Mixing incompatible greases can easily destroy a $2,500 breaker. Apply only in the amounts and locations specified.