Heh easy one. Go to folders: Scripts<Settings< and then open the ".nip" files you want. For magics it's "magics" and put // in front of items you don't want it to pick up. Same with the "uniques".

If you want it to not sell items, and just drop them on the ground then go to you character configuration file and edit this sections:

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Items identification configuration
// Note : Make sure that if you use a ID book, to place it in the no-stash area.
//================================================== ================================================== ===========================
// XP_UseInstantCheck = true/false Set to true to check items on the spot, instead of going to town for checking.
// Note : It will be ignored if XP_SellBackItems is set to true.
// XP_SellBackItems = true/false Set to true to sell items rejected by njip. If it's false, it will drop by the stash.
// XP_DropItems = true/false If you want to drop items when the gold is full, set this to true.
// XP_CheckInventory = true/false Set to true to check the inventory of crap items.
// XP_ShowStats = true/false If you want to log full stats of kept items
// XP_LogSoldMagic = true/false Set to true to log dropped or sold magic items.
// XP_LogSoldRare = true/false Set to true to log dropped or sold rare items.
// XP_LogSoldSet = true/false Set to true to log dropped or sold set items.
// XP_LogSoldUnique = true/false Set to true to log dropped or sold unique items.
//-------------------------------------------------------------------------------------------------------------------------------

XP_UseInstantCheck = false;
XP_SellBackItems = true;
XP_DropItems = false;
XP_CheckInventory = false;
XP_ShowStats = true;
XP_LogSoldMagic = true;
XP_LogSoldRare = true;
XP_LogSoldSet = true;
XP_LogSoldUnique = true;