The authors probably intended for the phrase to mean something like "this is how to come up with ideas for your writing." However, when subjected to interpolation and taken out of context (and word sense) as it is, "considering" could just as easily be seen as an adjective describing the types of "ideas" for the writing - "considering ideas," or "ideas of considering" for your own writing.
Yet, "considering ideas for your own" could just as easily be an adjective phrase describing the writing - it is writing primarily concerned with "considering ideas for your own." (This type of writing does not care about considering ideas for you. Rather, it recommends you do that on your own.)
"Own" is working particularly hard here considerating its (1) primary definition: Belonging to oneself. In this sense, the "considering ideas" are for your "own" (posession) = you get to keep the ideas. Or rather, (2) consider its secondary definition: Used to express immediate or direct kinship, where "own" could be "family" or "fruit of the loins;" - yes, this is "writing" regarding "considering ideas" for your own "fruit" (read: your flesh and blood).
But before you raise the issue, I am well aware that I completely neglected "for," a word that I have savored for the very end, for "for" is not only a preposition indicating "related to," but it could also be seen as a preposition meaning "because of," and in this case, the considering ideas are "because of" "your own writing:" indicating that the ideas under consideration are in this state as a direct result of the power of "your" writing (what ever kind of writing that happens to be).