There is no rule that will tell you whether a verb with an -ing suffix is a noun or an adjective. It depends on the context.
For instance, advertising is frequently a noun, but it also may be an adjective depending on when it is used.
Noun: They claimed that their targeted advertising was very effective.
Adjective: The advertising campaign was very effective.
If you have a question about the use of a specific -ing form in a particular sentence, please give us the sentence. People will try to help you decide which it is and explain the factors that help us decide.