Changing spawn rates in game?

[Arastiroth]

I was wondering how you can change the spawn rates for NPC's in game or if it was even possible? Also is there a way to change where an NPC spawns in game? I spent a little while looking around, but it doesn't appear to be any place that lists this information (at least, I couldn't find anything). It seems like #npcspawn update would change it, but it doesn't seem to do anything. Maybe I don't understand how to use the command or maybe I don't understand its real use? I know I can #npcspawn add to add spawns of a selected npc, but that then creates the problem of the mobs having VERY short respawn rates.

Also, can I add/remove items on an npc's drop list in game and SAVE it, too? I know I can do #npcloot add/remove, but I don't know how to save it.

Thanks for any help. =)