When to use ON or KUN pronounciation or writing method?

[Spirit Atlantis]

When do I use the ON or the KUN pronunciation?
One of them is original Chinese with a Japanese touch, and the other is originally Japanese.
Is there any other difference between them besides this?
And when to use which one when speaking or writing?(in hiragana/katana)
And which one is used more often?

 

[Elizabeth]

Do you mean for verbs, when do you use two ON readings in combination plus "suru" (for instance) versus the Kun form? Such as "kaijo suru" for release or cancel as opposed to "toku"? I start out by never analyzing it to that extent -- it's all just a matter of getting used to how words appear in their natural context. And once you can read kanji, the meaning should be evident either way.

 

[NANGI]

Konnichiwa Spirit Of Atlantis-san! Elizabeth-san!

I think "single Kanji + Hiragana or Katakana" is "KUN" pronounciation and "plural Kanji" is "ON" pronounciation. But "single Kanji" only is as the case may be.

NANGI