Speaking of what reading to use...
I use Raichan, I am sure native speakers don't need it so they don't know it. Raichan is an add-on for the internet browser (Firefox only). Everytime you pass the arrow on top of a kanji or kanji coumpound anywhere on the screen it opens a small "floating" box with the reading and meaning of the kanji itslef.
Now my question
Please don't ask me which ones, because I really can't remember, but I have notice that quite a few times Raichan for the same kanji compound gives 2 different redings (sometimes both using different 音読み and sometimes using 1 音読み and 1 訓読み). Since the translation is the same, why using two different readings for the same compounds and same meanings?