level 9999 for all main characters and a couple of character created max all skills and weapons for the main characters it took me a long time to max out the levels because I came back to play disgaea little by little after I originally beaten this game back in january of 2004
What can save time when leveling is throwing enemies into other enemies. Especially, when around rank 37+ items even if it's just a 30 floor one. It's only good some area if you throw all of the enemies into 1. For instance in you throw the mages in 11-1 into the pumpkin heads then you can get up 2x-3x as much exp if you were to kill 1 seperately. Plus If your not getting that exp bonus in rank 40 items it can be difficult. Every bit helps.