Clear Cache

Can someone explain to me how to clear cache safely?

I dont have anything in Cache folder, and If im correct if i will delete WTF folder my whole UI and addons setup will reset - and I dont want that..

I just want to clear NPC scan addon cache because i think it cached some rares even i dont have them.

Any suggestions?

Clearing Cache is just deleting the Cache folder, or emptying it's contents, same thing. If folder does not exist, wow creates it.
As for resetting the addon, doesn't it have an option to do so?
You can go to WTF->Account->Accountname->Realm name->Charactername->SavedVariables and delete every file that has NPCScan in it's name, i have only one file named _NPCScan.lua Deleting that might clear only that addon's settings.
Also, there's one more SavedVariables folder under WTF->Accountname->SavedVariables and you might wanna delete the NPC scan file in there also.

Well I have a cache folder ofc, but it is empty - always - so I cant clear it.. dont know why its empty...

And wierdly the only file I have in SavedVariable is blizzard combat log- even that I have a lot of addons.

Can someone tell me what is going on ? :)