you should have known by now how to read errors on your server monitor..
or else, your server will go down.
i'll teach you the basic's so Emistry can take a rest
usually, when you load an NPC script that is incomplete (custom or not) the errors shows up in the "log/map-Server_SQL.exe"
i'll give you an example of an error..
[Error]: sv_readdb: Could not process contents of line 948 of "db/re/item_buyingstore.txt".
there.. analyzing this error, it says that there is an error in "db/re/item_buyingstore.txt" in line 948.
in other words, this can be located in your ragnarok data folder inside db insde re and finally item_buyingstore.txt line 948.
now you know how??
now, if your script is done, put it on your npc/custom then edit your script_custom. put your npc there. oaky? i hope my little guide helps.
if you still don't get it, then wiki is waiting for you. and it wont be fun /panic /panic /panic wrahahahahaha!