I learn that NEXT is a crucial word in RV or Dowsing. Is PRECEDING a correct word? Coz I think PREVIOUS is too ambiguous.

Preceeding could mean any in the past. How about the word "last?"

They have to definitive words. Previous, Next, First, Final, Preceeding...

I will leave this for the response of the professionals. In my short experience in dowsing, I have not looked for things that have already transpired. I try to express my intent in as simple a context as possible. I'm not sure what your task is, but you may be doing fine with your wording. The community information says that you're in Hong Cong. Have you tried dowsing in your first language, if it isn't English? I think that would work best for you, if it works at all. This is what my logic tells me.

“Last” is generally too ambiguous for cueing. Do you mean last as in the most recent or last as in the future? Use the term “final” instead; however, depending on your cue, final may also be unusable because you are assuming there is a “final” something. I suppose I’ll have to ask specifically what cue you are trying to formulate

Actually I am trying to practice previous lottery draw dowsing so I don't know how to task!