If a pump is new or has been in storage, turn it over by hand to ensure that it rotates freely.  Periodically, check the mounting bolts for tightness.  Check the gearbox and fill it with the oil suggested by the manufacturer to the level plug or the level dipstick.  Check the oil frequently because too much, too little or too heavy of an oil may cause the gearbox to overheat.  Check the discharge priming valve and oil the pivots on the valves with external handles about every 200 hours.  Check the valve seat too.  Never run the pump with a dry seal.  The pump body needs to be full of water if the pump does not have a lubricator.  The Caprari PTO Pump pictured is an example of pumps being referred to in this post.